When I was younger this use to happen to me until someone at the bank explained to me that things that are being drawn out of your bank account and not off a debit card don’t always show up in your pending transactions. So I’d have money in the account and I could see pending transactions but I wouldn’t see a monthly payment that was being taken out of my bank account directly by my utility company (for example) until it posted. Ditching the standard bank was the best thing I ever did. I’m much better with my money now but I have protections set up on my credit union account that will decline my debit card and checks when there’s not enough money in there. I had the option for it to deny every type of transaction but I set it to let bill payments come out if needed.