Fido actually rings 20 seconds (4 rings) before voicemail picks up, not 15. This is a system wide settings, it also can not be changed.
it used to be changable until sometime in 2009, when someone out there thought that the number of complaints about people breaking the voicemail forwarding and complaining about it were simply too high rather than educating them about dialing the syntax to re-enable it, so they decided to hardcode it in the switch provisioning.
many of us advanced users would disagree with this change, as I really like the ability to control my voicemail delay or temporarily disconnect voicemail for a weekend trip, but fido nor its executives do not agree.
I timed it and it was 15 seconds for my phone (Samsung Galaxy Q). The phone would play the ring tone for 15 seconds and then it would stutter and then play the ring tone for a split second and then it would go into voice mail. At the stutter piont, I can no longer answer the call. I'll test it out again later (it's my wife's phone).
The rep I spoke to said he can change it to 20 seconds when I told him it was only 15 seconds. He told me to restart the phone after I get off with him to reset the settings. Maybe it's some phone setting. I use a custom ring tone (MP3 file).
have a look at the first line here:
I am a former programmer, and have programmed fido switches, I can CONFIRM the ring delay before voicemail picks up is 4 rings, which is approx 20 seconds. I was not lying, the actual value which is stored in the Fido switch is the number 20. Ask any one who works at a fido retail store, they will confirm this, unless they are new and do not read IQ.
What you need to be aware of is the 20 seconds is NOT what you hear, its what the CALLING PARTY hears.