Just to share - I did a ticket to AP upgrade in January 2020. I know it may be different when APs come back, but when I called Disney they told me they could not upgrade my tickets over the phone to an AP - they said I needed to do it at Guest Services in person. I think this is because they need to see your ID. I was able to upgrade my tickets to an AP with no issue at all in person at Guest Services, and I know you can do this at the Disney Springs ticket center.
This was also for a new AP purchase. I'm unsure if you're allowed to convert a ticket to an AP Renewal.