iPhone virus

My iPhone has a virus that causes it to shut down due to lack of battery power even though the battery is fully charged. The instructions from the Apple store and help desk haven't helped. Does someone know a way to get this virus off my phone?

Background: A few months ago I was searching the internet and suddenly my phone shut down, indicating the battery was empty, even though it was fully charged. This situation could only be fixed by charging my phone for a minute or two, which would reset the power to the actual charge. Initially, the phone only experienced this situation when I was on the internet but has since expanded to all functions of the phone. My phone now turns itself off while using any and every type of function, app, service, etc... (indicating battery power is exhausted).

I've backed up my phone and tried resetting it (as an entirely new phone not just resetting it to the default settings) as the Apple tech instructed but it hasn't helped. Can someone help me figure this out?

And, yes, I know iPhones officially don't get viruses but I can assure you they do. I've taken my phone to the Apple store where the techs said it had a "bug", not a virus. When I asked for clarification on the difference between a bug and a virus I was told, "iPhones don't get viruses". Whatever Apple wants to call it, it's a virus and it's messing up my phone.