Did any of the onsite tech visited your place to check the problem? If not, then demand to have an onsite visit since it is already 3 months issue is not resolved. Also, since you are not getting the subscribe speed you can demand bill rebate on the number of days your are unable to use the service.
LTE is much worse than WIMAX, and I agree to that. Wimax is a very reliable service that has been around for years while LTE has been under rigorious testing and improvement pa. LTE are not so much reliable kasi both Cellphones and your Home LTE are using the same Frequency, though, there are different APN and settings. This means that your HOME LTE is such like a mobile data also unlike wimax that uses special frequency.
Therefore said, it is much likely that your area is congested and LTE is not yet good. I still prefer Wimax, DSL over LTE as of the moment in almost all areas except some good areas that has really good and reliable LTE base stations that were ment to handle large numbers of users.