poor service from mweb sales.

I bought an MTN LTE-A sim from mweb and upon delivery I found that the sim card is not able to connect due to faulty telecom issues. I was advised to get a telkom LTE instead. Now I am being charged for both simcard. I have been calling mweb for weeks with no support. All they are saying is that I should pay. How can you pay for something you did not use