Trying To Charge Me Double

I booked with Regus and paid upfront for 10 days to use their co-working offices in Durban. After day 7 until day 10, their App started giving me problems when I tried to make a booking. I had to drive to their offices in order to make a booking and prove that the days I had paid for were not used up. I wrote to their accounts department and they never responded to my email. This was in January but until today they keep sending me invoices reflecting an amount owed by me and they have tried to debit my account a couple of times. I do not owe them and I am very disappointed by their dishonesty and bad customer service. Th offices I booked were in Umhlanga and Westville in January and my membership number was ***3