My experience of porting/transferring a number from Ooma > ATT Prepaid Wireless > Google Voice.
Began the process of porting/transferring a long-standing Ooma "home" number on Thurs., March 22, 2018.
--- Went into local ATT store on 03/22/2018 explaining that I'd like to get the cheapest ATT Prepaid Phone possibly with nothing fancy on the plan in order to ultimately port my Ooma-associated # to Google Voice. No issues. Got in/out of there for a total of $30.
--- Received msg. on ATT's site later on that day that the port request to get the Ooma-associated # ported to the new ATT prepaid wireless phone failed. At this point, a back and forth between myself, ATT, and Ooma began and this went on for several days straight. I was anticipating these issues, as most of what I'd read online from people that were trying to port a # *away* from Ooma had stated that it was a nightmare trying to deal with Ooma. I found this very much to be the case. ATT and I spoke numerous times, the # port request was resubmitted by ATT to Ooma numerous additional times, and those additional requests were all turned down again... about 4 times. I finally got ATT and myself and Ooma porting support on the phone together. For the longest time, all we could get out of Ooma was that the port request failed due to either missing info. or incorrect info. We asked them SPECIFICALLY what was missing or incorrect, and they never would/could give us a specific answer, simply reverting back to their bland statement that the port request was denied due to either missing or incomplete info. provided in the port request submission. A very helpful ATT representative finally got them to divulge that in the "remarks" section of the port request ATT was resubmitting, to put "Ooma, Inc." along with Ooma's business address in Palo Alto, CA in that same "remarks" section. That finally did the trick, with the port from Ooma to ATT being completed in another 2-or-so days. At the point of receiving the "completed" msg. on ATT's "port status check" page, I turned on the ATT prepaid cell phone for the first time and set the phone up and could indeed verify that my previous Ooma # was now associated with this ATT prepaid cell.
--- On Wednesday, March 28, 2018, I initiated a request in Google Voice to port the # from ATT to Google Voice.
--- On Friday, March 30, 2018, just under 48 hours from the port request from ATT to Google Voice, I received a msg. that the # was now associated with Google Voice.
All in all, the Ooma to ATT port was a nightmare and Ooma proved to be very unhelpful with the entire process until a very helpful ATT representative pressed them very hard for details on *exactly* how the port request needed to be resubmitted in order for the request to be carried out properly. The ATT to Google Voice port was very straightforward and completed with no issues.
Hope this helps.