Old username on portal

[#1]

I can't work out what's going on. A few years ago I was a PlusNet customer but switched to Virgin. I've decided to return and now have email and am waiting for a telephone connection.
When I try to access the website, my old user name is autofilled into the dialogue box and IO can't get rid of it despite clearing cookies, running ccleaner etc. It doesn't happen when I connect by smartphone.
Anyone know how to fix this?

[#2]

which browser are you using

[#3]

Firefox.

[#4]

From Firefox menu bar select Tools then Options then Security and finally Saved Passwords - is it there

[#5]

It was indeed there, I've now removed it. Thanks for the help.