Any phone call you get from your Internet Provider (ISP) should verified if they are saying anything even remotely dubious. Call them back on their publicly listed phone number, not one given by the caller.
In this latest scam they’re inciting fear from regular people by pretending that their access will be terminated if they don’t download some software. No prize for guessing that the software will be anti anti virus, right?!
While you should have anti virus software running it is not for your ISP to dictate which anti virus software you should use.