How to stop iPhone from accessing one Gmail account

iPhone 6s Plus with iOS 13.5.1. I have two Gmail accounts--one for work and one for personal use. I have always had the iPhone Mail app only check the personal account and never the work account. Last week I had to check the work Gmail account from the iPhone and so had to temporarily add the work account using the Mail app settings. After checking my Gmail work account I reset the Mail app to only my personal Gmail account and the Mail app only lists my personal account in settings. Problem is it keeps checking my work account and am receiving constant Gmail security alerts saying my iPhone now has access to my work email account. I want to stop this. I have deleted all my Gmail accounts on the phone and reinstated only my personal account, but the problem persists. The iPhone Mail app never actually picks up anything from my work account and seems to just be continually pinging the account which sets off the security alerts. How do I clear this setting off my phone and ONLY have it check my personal Gmail account?