unhappy with Incompetence and very unhelpful

I have a contract with MTN which was due to end in January,then went into store in February and asked what my last balance is of which I paid and they then told me that I need to call the call centre to get them to change from contract to prepaid,which I did.the next week I get an sms that 150 is still outstanding.The call centre is such a nightmare I called for like a whole week and was placed on hold to speak to some one for up to an hour and when I call the call centre the same thing occurs the automatic response tells me I should pay the arrears.Today I go in store and ask them why I was not not notified correctly when I came to make final payment they could not answer or help me I did advise them I have tried calling the centre but could not get help.i explained that I have not been able to use my phone the whole entire month,I have to borrow someone's phone to call the centre,but I was getting my smses and could use my cellphone banking up until yesterday,I was sent Fnb ewallet but did not get the sms for the pin I was then stranded.i was told they can not help me until I pay the outstanding amount or reopen my contract, and I must pay for this month.of which I am not liable