Bad service

So in november i took a contract with mtn before i could take it i asked the sales consultant if it's dual sim then she said yes,when i recieved it i realized that it is not dual i asked for it to be sent back they refused so i stayed with the phone,then i lost contract sim because most of the time i had to remove it and put my old one i reported that at mtn and i was told that i have to pay R160 for the lost sim or before i can get a sim swap.They were deducting R380 as per agreement for the phone and insurance then last month they decided to take R544 from my bank account now when they have to give me my money they are telling me stories ...i got a very bad service from them