MTN is nonsense

I changed my debit date in december to be earlier that month because we were getting paid early , and requested MTN to just change it for december. i will amend again in to the original date in january . Today on the 7th of january i call them to amend the date ,they are telling me their system is only giving them a date before i get paid . theres nothing they can do . I am so not happy with MTN i will not even renew my contract as soon as it exprires