There are no true Antivirus Products available for iOS/iPadOS. Those that claim to provide AV protection are little more than “snake oil”, have negligible (if any benefit) and for Apple devices should generally be avoided. Very often, Apps of this nature introduce more issues than added benefit.
Unlike traditional Operating Systems with which you may be familiar, iOS/iPadOS uses a sandboxed security architecture. As such, Apps cannot access any data outside of their own sandbox - and cannot access the storage and resources of other Apps. As such, it is impossible for an Anti-Virus App to scan the filesystem.
As for receiving multiple invoices, did you purchase/subscribe to TotalAV by paying through the Apple App Store - or instead directly with TotalAV via a website or from within the App?
If purchased via the Apple App Store, Apple may be able to help:
Request a refund for apps or content that you bought from Apple - Apple Support
Otherwise, if you provided your Credit Card details via a website or within the App, Apple will be unable to offer any assistance in cancelling any charges. In this situation, you will need to seek assistance from the Credit Card issuer.