The best method is to first contact TM. Ask them for a timeline. If they exceed that timeline (make sure you keep any correspondence record Eg email, live chat screenshot, case ID), then you will proceed to complain to MCMC @ https://aduan.skmm.gov.my/Complaint/AddComplaint?NOSP=1 There you can attach the case ID from TM and all the supporting information you saved. With all supporting documents, you will get prompt action from TM within 3-5 days. I did this for two of my accounts and both got upgraded finally.

At MCMC complaint website, choose the following options:

[attachmentid=9211783]

Credit limit is not for you to owe. It is for you to spend, that means if you have RM 800 limit, you can spend for RM 800. Not that you can accumulate your bill to RM 800 without paying.