Any way to remove +1 for phone number in autofill?

I fill out a lot of forms online and use Firefoxe's autofill to fill in my personal info. The problem I have is that autofill always puts a +1 in front of my phone number on the forms. Since the form is only looking for 7 digits, it chokes with the +1 and won't submit. This requires me to manually click on the phone number field and delete the +1 so the form will submit. With the amount of forms I fill out, this creates a lot of unnecessary wasted time constantly having to correct it. I have tried editing the phone number in autofill to remove the +1, and although it appears to do so, as soon as I save it, it comes right back again. Is there an about:config setting that will remove this? I don't know why Firefox thought this was a good thing and not allow a way to edit it out. Thank you for any replies