This happened years ago on my ISP here in Houston. They contacted me via phone and said my computer was spamming emails with viruses attached and took me off line until I corrected the issue. I ran a quick scan and they were right and I had a nasty virus on my PC.
I've had this with Rogers before, they are idiots and there can be a lot of false positives. In my case it was Remote Desktop I had setup which they flag as a remote administration malware.