Nonsense customer care and lack of accountability

I have a contract with MTN, and we have agreed that they debit on the 25th of every month, now they failed to debit end of May and they are not taking accountability that the failed to debit, now they want to debit twice without considering that it is not my fault that they failed to do their job and debit on the agreed date. The consultant was even forcing me to agree that I received an alert and I should contact my bank, but I checked on my statements and no debit order came through on the 25th. The are just fill of *****nse and i am highly disappointed as their service is ****.