MTN sim Replacement

The poorest service ever received, since getting the MTN sim replacement for the cell c one I have had no internet....logging calls is futile as no reference nr is given and the best answer they can give is to change network to 3g and reboot router...wait 5 and then change back to 4g and reboot...error received is "incorrect profile"...pretty sure they have no idea how to troubleshoot their APN configs....this is not a MTN issue