Vox WiFi seriously lacking aftercare

Vox installed a router and activated the WiFi after Vumatel had redirected the fibre to my unit. Vumatel came without a ladder, stood on our kitchen cupboard and broke a shelf. I showed the Vumatel person where I wanted their unit to be and when I came back in from the garden he had installed it firmly elsewhere. Vox was most professional at first - they sent us a photo of the person who would install the router - he came on time and was most professional. The after service is shocking though. I am a teacher and soon realized that the strength of the WiFi is lacking when working via Zoom with my students. My husband have made many futile phone calls and wrote emails - all we want to do is go for a more expensive package and stonger Wifi strength and they just are not coming back to us. This is most embarrassing as I keep telling the parents of the students I now have to teach online that I am in contact with Vox and that the problem will be sorted asap. Yet it is not being resolved. Pleaseee help. My account number is *** We have been referred to Clinton Green who is apparently our account manager. He is never available and does not respond to messages.