Hey @kamram1 and welcome to the Community!
I like to start with the basics, so pardon me if these sound obvious
- Does your phone show signal bars? If so, how many and what does it show for the network (LTE, H, 3G, E...)?
- Have you tried restarting your phone?
- Are you able to place calls from your phone?
- Did you change anything in the call settings on your phone? If you could let us know which model phone you're using, we can help you out with where to check in the settings
Let us know!
I'm afraid i haven't been able to fix the problem.
My phone has full signal bars and it shows LTE for the network.
I've restarted my phone three times already but the problem is still there
I can place calls from my phone, and sometimes my phone moght even ring for specific numbers but other times it doesn't
I haven't changed anything in the call settings
Ive heard about this happening to people but no idea on how to fix it
Is this a new issue with your phone? That is, had it been working properly before but only recently started having the issue? Or did you just get the iPhone 5s and ever since you've been having problems?
Does your phone show a missed call as well? If your plan has Who CalledTM, do you receive a notification you missed a call -- in addition to the voicemail?
To your knowledge, are you having the same issue everywhere or only at certain locations? I understand your phone shows full signal for LTE. However, phone calls (with the exception of voLTE) are transmitted via the 2G and '3G' networks. That's why people notice their phones switching networks when making/receiving calls. Depending on your location in relation to the cellular towers (and their bands/frequencies), it's possible the 2G and '3G' signals reaching your phone at that location are weak. I understand you can place calls, but that would also be location dependent. Have you tried to disable LTE? What network do you connect to and what is the signal strength? Do calls also get sent directly to voicemail? You can get an idea of your surrounding towers here.
It's also possible that the phone has issues switching networks. I know the iPhone 5 had network switching issues (see here), though I'm not sure if the 5s has similar problems. I understand you restarted your phone numerous times, however have you attempted to reset the network settings? Settings --> General --> Reset --> Reset Network Settings
Does your phone have the most recent iOS?
If you had a different phone previously, perhaps Fido (customer service or moderators) could reprovision your phone.
Hope this helps