Gems skip deductions intentionally.

Im a member of Gems Medical aid, member number : ***. I'm also a retired government employee. Gems is deducting R2800 every 1st of the month. On Wednesday I received a massage from them saying they were unable to debit my installment because there was no money and that was not true at all. Every month I make sure that I wait for my debits to be paid. I only use the money on the 4th of every month. Now they are telling me that I need to pay it on the 1st August . Now tell me how can I afford to pay the whole amount of R2800 on the 1st August what is worse is that I didn't get a budget for this. I just want them to make a plan because it's their own fault. Please you did help me before from this same Gems. I have nowhere to go for help.