I read that if you run out of credit on your three payg sim you can still receive calls on it. So I have an iPhone and all I ever use it for is the running app ismoothrun. I don't want to make calls or use data so not worth paying £15 per month. I connect the phone to my wifi when I get home to upload and save my run to the servers. Problem is now and again the phone loses gps signal from the satellites during and then my run my pace is normally messed up at the end, usually much faster. So I wanted the sim to just use the phone masts to acquire a location signal if the satellite signal fails. Is this possible since it is supposed to still receive calls?