WHY DON'T I HAVE SIGNAL??

Okay, so according to the coverage map, I have Telkom Mobile signal everywhere I usually go. However, going back a few months, there would come weekends(that will continue through to weekdays about 3 days at a time) that I will simply not have ANY signal. Nothing! My phone would show 3G but no signal bars. During these times I can not MAKE CALLS, RECEIVE CALLS, SEND MSGS, USE THE INTERNET or anything of the sorts! The only time I can use my phone is if I'm on Wifi and use messaging systems that work through the internet. This past Saturday my signal just went out the window again and I am once again in a situation where I can barely use my phone even though I pay Telkom to be able to use my phone. I have business, studies and family matters to take care of and you don't allow me to do that anymore. No, I have not changed any settings, and no I have not wandered out of areas where there usually is signal. I find this truly frustrating and am seriously considering transferring to another service provider if this situation can not be explained to me and someone can assure me that this will not happen again.