Does it display the same issues on ethernet cable connected devices - or is it just wifi? If so... what devices specifically are struggling - and what Hub model is it?
If your Hub isnt working properly then the first thing to do is to call it in a fault and see what they say when they check your connection.
Or is that what you have been doing ?
If so, You can text VM on 0753 305 1809 include account name/number and what the issue is, there is also a “Chat” option on their website - but note that replies usually take longer. Or you can speak to the team on WhatsApp by logging into your online account via a mobile handset and there will be a link to speak to VM by Whats App (the number is 0780 3089 684 ) - you can use the same number for their other social media platforms too (TwitX/Fbook. etc) - so try them all.
FINALLY… A VM person will pick this up on here and respond, but it can take a few days for them to get here.