I received a similar call both yesterday and today from a similar number.
An Indian-sounding man claiming to be Alex from the Virgin Media Technical Department.
Yesterday he asked "how are you" and hung up when I said "not so well".
Today he said "you are having problems with your broadband? Sometimes fast and sometimes slow?" I said "no it's fine" and he hung up again.
If they call again I'll put on an old lady voice and pretend it's all very complicated to try to waste as much of their time as possible.