I would be very wary of log4rescue. Google shows 4 hits for them - two from their own website, one from this thread, and one totally unconnected with the firm.
Their website mentions lots of growth and about 800 employees.
While that's possible, I can't imagine a growing web company with 800 employees and only three relevant Google hits.
They may be totally legit, but...
Their domain was registered on 17 Nov 2009, so they aren't long-standing, and their registered location is Calcutta.
Did the caller say how they got your details? Did he/she have more information about you than you'd send to MS?
Saab's answer may be a tad drastic, but it will fix it.
I'd be inclined to run Malwarebytes and see what it finds. Some of us on here may be able to "talk you through" the disinfection process. I've done a fair few (mostly not in my own PCs), and some are real experts!