Using Access Form vs Billing Modification

We have 3 paid levels (monthly, annual, and site license), all based on recurring charges with Authorize.net (and we have s2member Pro). Currently we are only using the Access forms.

I’m unsure what happens to someone’s account if they have a monthly membership and then (while logged in) they sign up for an annual account. I would expect:

1. The Role to change from Level 1 to Level 2
2. the EOT date to update to add one year beyond the current EOT
3. and for the recurring billing to be updated to the new amount (or remove the old recurring billing with authorize.net and create a new one

Will this happen if we just use the normal access forms? Or must we use the Billing Modification forms?

(The docs sort of imply that we have to use billing modification forms, but it’s not entirely clear to me, and I’d rather simplify and use the forms we already have.)

Thank you!

http://wordpress.org/plugins/s2member/