@jthomas2 , I use Chrome.   To get the private browser there, you click on the 3 dots up top, on the right, next to the address bar and click on 'New Incognito window'. 

For Explorer, click on the same 3 dots and click on 'New Inprivate Window".

But pretty sure none of this will fix your issue. Best bet would be to contact "support", as frustrating as that is, and have them look into disabling the online bill pay. 

Good Luck.