Hello MOJ1,
Welcome to the community!
@MOJ1 wrote:
...Huawei RIO-L01
EMUI version 4.0
Android version 6.0.1
...
· Network
LTE – B1, B3, B7, B8, B20
3G – 900 / 2100
2G – 850 / 900 / 1800 / 1900
Are you sure that is the version of your phone? Something is not quite adding up... According to those specifications, that phone has both of the compatible bands/frequencies for 2G and none of the compatible bands/frequencies for '3G'. With regards to LTE, that phone only has one compatible band/frequency, band 7 or 2600MHz. You can verify the compatible bands/frequencies here.
I understand you said the phone was working perfectly fine and data would go to 3G on Chatr. However, since that phone does not have any of the '3G' compatible bands/frequencies, it shouldn't have been able to access that network. I also understand it may have been a typo and you might have meant 4G or LTE. But Chatr does not offer LTE, they only provide service on GSM (2G) and UMTS or WCDMA ('3G'). So you should have only been able to use 2G with them. Data speeds with Edge (2G) do not usually allow for adequate streaming of Youtube videos.
You noted the phone updated from Huawei recently. Is it possible the phone updated the software/firmware for a different version of the phone? Was it an over-the-air update or done via computer? If an incorrect software/firmware was used, it could account for the troubles you note.
You also noted that your phone goes from 4G to Edge after some time. Is that while you're using the phone for data or on its own? With the exception of voLTE, voice calls are sent over the 2G and '3G' networks. Generally, phones would standby in a data connection (4G or LTE if available) and switch networks when making or receiving calls. Unlike UMTS (WCDMA), the GSM network is not capable of simultaneous voice/data. Is it possible that the phone was switching networks to receive a call? Have you missed any calls during that time?
Additionally, coverage depends on the availability of matching bands/frequencies on your surrounding towers as not all towers use all bands/frequencies. You can get an idea of the location and bands/frequencies of your surrounding towers here. Even if there is a close-ish tower, cellular reception might get obstructed by buildings, trees, etc. since the higher frequencies travel the shortest distance and have the least penetrative ability (see illustration posted here). Depending on your location, it's possible that the 2600MHz coverage is spotty and the phone switches you to the stronger 2G signal.
Hope this helps 
Cheers
Hello again,
Where did you find those specifications for your phone? As far as I can tell, the G8 Dual-SIM has slightly different specifications. These are the specifications for a dual-SIM version:
2G bands:GSM 850 / 900 / 1800 / 1900 SIM 1 & SIM 2
3G bands:HSDPA 850 / 900 / 1900 / 2100
4G bands:LTE band 800 / 900 / 1700 / 1800 / 1900 / 2100 ~ taken from here.
Admittedly, that site does not provide the model number for their particular dual-SIM version so these may not be the actual specifications for your device. That said, they do explain how your phone was able to access the '3G' network with Chatr.
Assuming those are the specifications of your phone, it would have one compatible band/frequency for LTE, band 4 or 1700/2100MHz.
According to those specifications, the phone is a dual-SIM dual-standby device. With such devices, only one SIM can support '3G'/4G at a time. The other SIM will limited to GSM (see downloadable G8 FAQ PDF file here). Since both SIM slots in that phone are capable of 4G, it doesn't matter which slot each SIM uses. When the Chatr SIM becomes active with '3G', it will switch the Fido SIM to 2G. **edit** I suspect that when you manually reset your Fido SIM to 4G, you're making that SIM the active '3G'/4G slot. Doing so, in turn switches the Chatr SIM slot to GSM. The Fido SIM slot probably wouldn't be able to automatically switch to 4G in case data use is needed with the Chatr SIM**
If you wish to only use Fido for data and Chatr for voice/text, you might consider trying to limit your Chatr SIM slot to 2G-only. While reception on 2G might not be as strong as using '3G', it should still be adequate for voice and/or text. It might also prevent the Fido SIM slot from switching to 2G.
With regards to the over-the-air update, is it possible that your phone updated the wrong firmware/software? If your phone was bought in Pakistan, the proper update may not be available in North America.
**edit** I understand it seems strange that both the dual-SIM and single-SIM devices would have the same model version labelling. However, the dual-SIM section of that FAQ notes: Shipped RIO-L01 phones include both single SIM card and dual SIM card versions**
Hope this helps
Cheers
Hello again,
Okay, those are the specifications you noted previously.
Unfortunately, there is no way to undo an update. However, if you can find the proper firmware, you might be able to reflash the software. The tricky part is finding the correct firmware. These sites here and here show links to the Middle Eastern Marshmallow version firmware. This site shows the Ghana Lollipop version firmware, while this site shows the firmware for the European Lollipop version. I have not found any specific version from Pakistan.
Using the improper firmware version might cause issues on your device. Addtionally, if done improperly, it could render the device inoperable. If you do decide to follow this route, you might consider familiarising yourself with such procedures and determining the proper firmware required by your device.
If the issue is actually the result of a weak 4G signal issue, have you tried to use the phone at other locations where 2600MHz might be stronger? If the phone switches to 2G because it's stronger, it's unlikely to switch back automatically until it receives adequate 2600MHz.
**edit** Just so we don't miss anything... since your phone is LTE-capable, it should be using ltemobile.apn**
Hope this helps and best of luck!
Cheers
