The ringtone works fine and is turned full up. The problem is when someone phones it doesn't ring at my end, but does at theirs, then eventually to voicemail. This happens about 3 calls in every 10.
I can phone my mobile from my landline and it will ring perfectly. I can then hang up and ring it again, the landline will have the ringing tone, but the mobile won't be doing anything, then voicemail answer, if you leave a message the iphone will then inform you that you have voicemail.
I have researched it on the internet and I am not the only one having this problem with ios6. The problem began the second I upgraded from ios5 to ios6.
I have even put my wifes sim in the phone to see if that cured it, it didn't. My wifes iphone is still running ios5 and doesn't do it, she refuses to upgrade and I can't say I blame her.
I think this will be my last iphone, it says alot when they can't get the software righ and don't appear to be doing anything to correct all the faults ios6 has.