OVERCHARGED FOR NOTHING AND REFUND REQUEST

I have got a contract which was transferred from Nashua to MTN , and my monthly subscription was suddenly changed in march this year. I never add on any data , but was being billed for extra data which l am not getting and called call center many times .They promised to solve it but still nothing happened , to rectify it . They call me saying they will close my line if i don't pay. i am seek and tired with MTN, since they took over my account i am having problem after problem every month.<br> <br> Secondly , i want a refund for the money i have paid for November to them thinking that the invoice i paid was for them instead of Nashua Mobile because they took over on the 1st of December. If you check my account is paid in advance now, like the invoice for April is due to be paid on the 22nd of APRIL BUT MY ACCOUNT IS PAID ALREADY in advance hence i want this refund for this amount so that I can pay Nashua Mobile for the invoice of November which was suppose to be paid to them but was paid to MTN.<br> <br> I want this refund so that i can pay Nashua, my account is due to be paid on the 22nd of April at MTN.