21 days policy changed to 39 days and the phone is missing.

One of my contract phone was booked in on the 22 February 19 (OBF). We enquiry on 26 March 19 and only found out it was courier on the 17 March 19. Once again we enquiry what is happing to the phone it has been 21 working days waiting period, we were informed that they do not know where the phone is. This is unacceptable for me and deeply disappointed in MTN service that am receiving, I have been with MTN for years, does this mean I need start look for different network provider? Hope to hear for you ASAP for the solution of the phone.