Shocking service after moving from ADSL to LTE -Paying for a service we are not receiving.

We received a call from Telkom to say that they wanted us to move from our ADSL line to LTE as they want to move away from ADSL because of cable theft. They make all the promises about better connectivity and speeds. So we agree and they send us a new router and sim card and we set it up. Our ADSL gets switched off and our LTE router goes live. We are extremely impressed because on day 1 we have phenomenal speeds. Day 2 no one can connect as the speeds are now running between 100kbps to maximum 1mbps. Needless to say we cannot do anything, no emails, no netflix, no wifi for our phones. We have phoned Telkom numerous times to get it sorted. Everyone make us switch off the router, change settings from Auto to Manual. Nothing helps. We have been promised 3 times that an internal technician will contact us to help us resolve the issue but nobody ever phones us back. So after being on LTE for about a week we have only had 1 day where we could actually use it. We are paying for a service we are not receiving. They refuse to move us back to ADSL where we had no issues, we could watch live streaming, have all our phones connected plus more and still ran between 8 - 10mbps. There is no help at all to rectify this issue and it is now getting ridiculous. We pay for internet because we need it and now we are not getting it. We were happy on ADSL. Fed up with this ridiculous service and nobody seems to know what to do to fix it!!!