Try calling it in as a fault (on 150 VM line - or 0345 454 1111 others) and see what they say when they test your connection - n.b.- the UK call centre is still picking up and calling at 08.00 (Mon-Sat) or 09.00 (Sun) gives the best chance of getting through quickly.
Try this though...
Go into the Hub3 settings. Type in http://192.168.0.1 into your web browser’s url box and login with settings password on the Hub's base sticker (or your own if you changed it). Then in Advanced>wireless>smart wifi - tick the disable “channel optimisation” box and save settings. Then, go to advanced>wireless>security, rename the 2.4 & 5 GHz network ssid's. Just change 'em to whatever you like and something that will differentiate them (e.g - xxxxx_2 & xxxxx_5) -- use the same password for simplicity, Then, apply settings and restart the Hub. Your 2 wifi networks will now be clearly separated - and you can then select the network you want to connect to individually from the "available networks" list on each device.
Note all your wifi devices will need re-connecting to the new SSID's and passwords.
5 GHz is always better/faster and subject to less interference (and is better for iDevices ) than the 2.4 one - although the 2.4 one has the better "range" and some older/cheaper/dumber devices can only use this one.
You should also use a wifi analyser App to check which 2.4 channels are being heavily used around you and move yours to one of numbers 1,6,11 that is least so, but it wont help if there is other interference.
See if these changes help - you will lose any “seamless roaming” benefits but it may not matter and you can always change the settings back by doing a " pinhole factory reset " if you prefer the way it was - or it doesn’t help.
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.