Yello MTN - please can I pay you by EFT?

Despite me trying to pay my monthly contract premium to MTN by EFT on 5 occasions in the last three days, my bank sends a message: Ïnvalid Link Recipient Number Error code:12. I have now spent days communicating with MTN Customer Care staff who have asked me to change the same details (Account Number and Cell phone Number) on the beneficiary section - all with the same result. My bank tells me that they have received this same query from other clients. MTN - please investigate.