Problem with buffering

So we are on Big volt bundle package. 4 people in the house all with devices, we complained at Christmas as when trying to watch films it just kept bringing up the circle of doom and pausing the film. We spoke with virgin and after several phone calls and rebooting the system they decided we needed a new router as it was outdated. The new one appeared to be ok but after a few days all started again. If daughters are on ipad/youtube we can't watch anything without constant buffering. Virgin say it's ok on tests but phone's constantly dropping to 4g so WiFi very intermittent. Hubby couldn't watch virgin TV yesterday morning and we have to constantly restart the box. My contract is due imminently and they're putting the prices up again. Just wondering if anyone else has this problem or wondering whether to switch supplier, been with them a long time but this is getting ridiculous now. I read in a earlier post that someone had sky and never had a buffering problem but now they've switched to virgin they have 🤔