Unfortunately this is a very common SCAM... while they sometimes claim to be from a particular hardware manufacturer (such as DeLL), more commonly, they assert that they're calling from Microsoft.

Regardless, it's a SCAM, and you need to know NOT to allow them any access to your computer... nor to pay them anything (do NOT give them any credit-card nor bank information).

There's very little that DeLL/Microsoft can do, since these scammers can set-up-shop and call from anywhere.

Neither Dell (nor any other vendor) nor Microsoft, nor anyone else can remotely determine that your computer is infected.  Nobody!

All these "cold calls" are scams.

I recently read where North American scammers have joined in, hoping that a familiar accent might foster trust. Just hang up on these criminals.