Early debit of contract resulting in unpaid fee

Good day I have a contract with Mr P Mobile and i advised them when i t**** out the contract that i am getting paid on the 20th of every month. In june they decided to take the money on the 19th of June due to the 20th being on a saturday - HOW DO THEY EXPECT ME TO BE PAID A DAY EARLY. i was now charged an honouring fee of R90 on my account due to there being no money at the time of there debit order being taken - THATS IS WHY I TOLD THEM DO NOT TAKE MONEY PRIOR MY PAY DAY.<br> I would like the honour fee of R90 refunded back to me - urgently