Poor service from Accounts department

I am a customer of Courier guy for the past year now and lately getting no joy out of them. I am making payments so they can credit my account in order to book out parcels and I have been asking 5 times already (just today) to allocate R750 to my account.

They are quick to deduct money from my account but for the past 6 weeks I have been begging and nagging with every payment to credit my account so I can carry on with my business and actually make a living.

Linda, I believe a manager in accounts department said I should send the proof of payments to her directly for moneys to be allocated and still no joy. It is just adding to the problem because now I need to send it to Linda and the general Courier guy e-mail address still to get asked to send the proof of payments again or just sending me the same wrong statement.

If this is not sorted shortly, I will cancel my account.