MTN Bad service

After being with a loyal client with MTN since 1997 an *********** sales agent called me for a upgrade and informed me with the incorrect upgrade info just to do the sale. I am struggling for 4 days now to get my upgrade sorted out after speaking to so called managers. Who promised me to have my query resolved and two days later it is not resolved. I’m using my phone for business and now have to ask clients to call me. MTN, is this how you treat your loyal clients of 24 years?