Paypal I Changed the Preffered Payment Method before purchase

Wanted to purchase four items from Ebay using Paypal like I have for years without any problems. I did not want to wait 3 days for my bank transfer so I changed my preffered payment method for Paypal to take my money directly out of my checking account(different account). Confirmed that my chaecking account number was changed by refreshing the page. Felt good about making the purchases and did. The next day, Paypal attempted to take out of the old account(original account) that I changed from which made me overdrawn since there was just a few dollars in that account. Then 3 days later they tried again making me $120.00 overdrawn. The purchases on Ebay only totalled about $75.00. Somehow Paypal got about $10.00 out of something and now owe Paypal $64.00 plus the $120.00 my bank charged me for the overdraw. I tell Paypal all of this and they say it could not happen but it did. If I could NOT go ahead and purchase Paypal should of had another screen or pop up that says something, to wait or something? But all indications on my side said the Preffered Payment Method had changed.