Incompetence and negligence

I sincerely do not understand why i should always remind Vodacom to debit my account, we have an agreement to debit my account monthly however because of incompetence i presume, my account is not debited again. should i pour petrol, drive to the nearest branch and do a manual payment hence we have agreement of monthly debiting. Who's going to refund my petrol? what's the point of having an agreement whereas you're not going to keep your end of the bargain. i regret why i did business with vodacom, when my contract is finished i ain't renewing it, never.