Mtn is not the cellphone service you want to use

The worst customer service experience I have ever received from MTN. I have been paying for an MTN cellphone contract for almost a year now, but the service I am paying for is still not fully functional. The problem is that only people who are also on the MTN network can phone me. Anyone using another cellphone network simply cannot get through to me. I have contacted MTN numerous times, both by phone and by visiting their stores in person. Almost a year later, I am still paying every month for a service that I cannot properly use. This has become more than just an inconvenience. I have a 7-month-old daughter, and because her school cannot contact me on my MTN number, I have had to carry an additional phone with a different cellphone number just so that the school can reach me if there is an emergency or if they need to contact me about my child. How is it acceptable to pay for a cellphone contract every month and still not receive the basic service you are paying for? What is even more frustrating is that nobody seems willing or able to take ownership of the problem. I am constantly redirected to someone else, only to receive no solution. I am extremely disappointed with MTN and their customer service. This has been going on for almost a year, and I simply want the service I am paying for to work. MTN, please take responsibility, investigate this properly, and FIX THE PROBLEM. I should not have to carry two phones because the network I am paying for cannot receive calls from other networks.