Phone suspended although account is not in arrears

Since I have upgraded my phone in October 2015 with MTN they suspend my service on about the 3rd or 4th because my subscription cost exceeds my credit limit with MTN. this means on that without me making out of bundle calls or using out of bundle data my account gets suspended because I exceed my credit limit. My subscription gets paid on the last day of the month via debit order for the full amount but then on the 1st day of the next month the new subscription gets debited to my account which then exceeds my credit limit so both my phones get suspended 2 to 3 days later.<br> What is the point of having a cell contact like that. Phoning the customer care centre is useless because they just send an e-mail to the credit department because apparently the credit department can only be contacted via e-mail.<br> As according to MTN I am not credit worthy enough for my subscription fee they must then cancel my contract of my second phone immediately so that I can move to another service provider. It is a pity because I have had these two contracts with MTN for more than 12 years and I have never had my phone suspended due to non payment.