Zoom fibre poor service

I upgraded my fibre to 100mbp end of February 2025 and ever since I have never got the correct speed, when I run tge speed test it gives 12mbp and that is not what iam paying for. I have been calling and they have been closing my ticket with no resolution I lastly spoke to shereen from zoom fibre and she is telling me she can't assist because I don't have a LAN cable. The speed I am getting should not be affected by connecting wireless or with a LAN cable. I am working from home and these people are putting me in jeopardy of losing my job because iam not compliant with my internet service. I need this to be resolved as soon as possible. ZOOM FIBRE HAS HORRIBLE SERVICE VERY PATHETIC HOW CAN I BE PAYING FOR SOMETHING AM NOT RECEIVING FOR 2 MONTHS