I've just had an obviously fraudulent phone call, purportedly from VM technical department, sympathising with the poor service recently and offering to connect to my router to improve throughput. The first call came from 08089 024496 and, after the characteristic short delay that seems to indicate a cold call, a very oriental sounding lady began speaking. The quality of the call was so poor, however, and the connection kept fading out, so she asked me to hang up and called me back from 01406 857908. (This was another indication that it was a scam - VM shouldn't have poor quality phone lines or have to ring back from such a very different number).
She talked me through connecting to speedtest.net to assess my network speeds, (which seemed adequate: 207.06 down, 20.75 up with a 9ms ping). She advised that the upload speed should be between 50 and 80, the download speed should around 280 and the ping should be around 15 - another howler.
She then asked me to open a Run dialog and type in hxxps://join.zoho.com/176827019 to allow her to connect to my router and sort a few things out. She suggested that the final number was the unique identifier for my router. This would've opened a remote support session, giving her or a colleague remote access to her PC, from whence they could do almost anything.
I refused to make the connection, at which point she rather petulantly told me that if I wouldn't comply then she couln't help me and hung up.
Don't be taken in. I'd be shocked beyond reason if VM - or any ISP or IT company, for that matter - had enough staff and time to instigate a call to a customer to cure a problem the customer hadn't reported.
Don't be taken in. Just hang up. Be safe.
P.S. While writing this up, I had another call from 01444 215877, but this one didn't start the conversation when I answered. I don't know whether they target people in the same area code in a batch, but I'm in the Southend-on-Sea area of Essex. Beware!! Don't let them ruin your day.