VM has always had its own PSTN and will continue to have its own phone system, no reliance on BT. I was a subscriber of a main predecessor company - Telewest - which installed its own telephone exchanges in 1993 using the DMS-100 system from Northern Telecom, and it was the first UK cable TV franchise holder to do so.
You will continue to be charged for this phone service as it will still cost money to run even without the phone wires.
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Hub 3.0, TP-Link Archer C8, TP-Link TL-SG108S 8-port gigabit switch, V6