MTN lack of response

I asked MTN to e-mail me my monthly invoice for telephone number *** as I file them in a folder on my computer. This they now do and I have to use my ID to open the attachments. Unfortunately my ID as password is rejected. On 31 August 2020 I e-mailed their customer service about the problem. I got a computer generated reply with reference *** promising reply within 8 business hours. No reply so I mailed them again on 3 September 2020. Again computer generated acknowledgment with new reference *** and to date no reply. This morning I spoke to someone in their customer service department and was told to phone again in 2 hours as their system is slow, I doubt if that will help as they don't seem to understand the problem.