POOR ACCOUNT SERVICING

I have had an Edgars account for the past 43 years. Their accounts have been taken over by RCS Group and I have experienced endless problems with payments made to the account via EFT do not reflect. I have to send emails or call them to enquire why this is happening and the payment then suddenly appears on my account. I object to the fact that I am being charged interest on the "outstanding" balance when payment has been made. The Call Centre are quite inefficient and not of any help. I wonder if "non payment" of an installment would be ignored as much as a payment???????