DOUBLE CHARGES

Can you guys check your system correctly when you processed debit order, this is the 2nd time being over charged, I missed the payment last month with was paid paid last week and proof of payment was sent to them to update the records which was not being done as now they deducted more than they should and it is going to mission and half to get refund and if I dispute debit order again is going to a struggle to get it, can someone tell me what to do because is getting frustrating,AND NOW I CAN EVEN GET HOLD OF FINANCE DEPARTMENT