Terrible service

My Sim card I received with my contract phone, wasn't even 2 months old, then it started giving problems. It started showing emergency calls 4 days ago. Each time I called into the call center, I was told something different was wrong with the Sim card every time. The last day I called in, the agent suggested I go into a store and have my Sim card tested, if it is the Sim that's problematic, they would have to do a Sim swap. I then asked would there be an fees I would have to pay, I was advised that because I didn't lose the Sim card or break it, I shouldn't pay because it was clearly a faulty Sim card I was given. Took time off from work to go to a mtn store, to have my Sim card tested, and then I was told I should get a Sim swap, and because it's a contract phone, I have to pay the fee. My only problem is that I've been told each and every day i called into the call center, something different was wrong with my line and I've contacted mtn through every possible platform there is, with no useful feedback. I made use of these platforms because I was unable to visit a store inside working hours. It caused me a huge inconvenience, since I could not use my cellphone at all.