Because of the price hike you can cancel the contract with 30-days notice and no £ penalties and find a new provider. When you call in to do that they may offer you a better deal to convince yoiu to stay - or they may not!
Alternatively you can grab hold of the Wifi issue and sort it once and for all for yourself. Ignore boosters and assuming your wired connections are all ok, then getting your own wireless equipment will solve any wifi issues permanently, and will be transferable to other BB suppliers kit should you move supplier.
Get either.....
(1) A Mesh System, (2) A Wireless router, (3) A Wireless access point or (4) A combination of (2) & (3).
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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.