Too Much time on the phone

I have a number of issues with this so-called service provider, but my latest one regards payment. They have a debit order in place and debit my credit card every month. On the 1st. I get a call saying there weren't enough funds in the account, which is nigh on impossible since it is a credit card with a very considerable limit. I check my numbers against their, and they are correct. What this tells me is that their system has failed to work. This is not the first time. I changed my credit card details in September and gave them the new details over the phone and was told it was okay. And according to the data read back to me it was correct, so how is it that they now claim that I didn't have enough funds. And when I try and call, I get a customer service centre and the unbiquitous computer call selection with Desmond Dube's voice. I want to speak with a senior executive about the crummy service, but there seems to be no way to actually speak with a person! Useless service.