RCS game card apparent non-payment

Very unhappy with the service. I PAY my RCS Game in CASH in advance then I keep on getting call to say I am in arrears. I phoned and was told that i can ONLY pay CASH on the 1st of EVERY month. CASH PAYMENT made day before the 1st wil be seen as an attempt to settle the account quicker and not as a monthly installment and you are in arrears with a penalty fee although your payment is there. A CASH payment after the 1st will be considered arrears and a penalty fee is added which puts your account in arrears again. How fair is this? No grace period or no opportunity to request or suggest a CASH payment date which suits you. Best to settle in CASH and get rid of this ******* company *****ing money and living Game Stores a bad name. Any other suggestions regarding all my lost arrears fees?