Contract upgrade

I have a contract with Mtn now is time for an upgrade,Dsv keeps returning my product back to the warehouse now I calling Mtn to assist on why my product keeps returning back and is there any other way I can get a different courier since Dsv keeps returning back my product they say no way go get help in stores but that in-store keeps returning me back to doing it online iv done this for the 4th time and I'm tired of this back and forth is there any other way to be assisted?