iPhone was blacklisted by Verizon and got it removed from the blacklist

Thank you to all the responses on this thread, it really helped as I navigated the same type of situation. Successful resolution (I think, we'll see after the 72 hrs!)

My husband and my apple watches never were able to successfully connect to our digits paired cellular plan on T-Mobile after we switched from Verizon and it's been crazy to try and backtrace the reason. Long and short I bought the devices from Apple and only had one carrier before T-Mobile (Verizon). A tech rep from T-Mobile told us we needed to switch to a stand alone plan to make cellular work which thankfully I knew enough to not go down that rabbit hole. We want our watches to work as if they are our phones when the phone is off or far away and a standalone plan requires a whole different appleID/seperate phone number.

Another rep realized the imei numbers were blocked and that it had to be either Apple or our prior provider Verizon since the lock could not be placed on their system unless the watch was purchased through them, they transferred our call to Apple and they checked and the phone was fine on their end, unlocked and good to go. We called Verizon and got a customer service rep that checked but we had to find an old 4 digit pin for the deactivated account to go any further. Once we found it she said it was unlocked and not definitely not their problem--told us maybe it was a sign we needed to switch back to Verizon. Called T-mobile again and they said it definitely is Verizon's problem and unfortunately we needed to reach out to them again. TMobile agent checked our iMei numbers on Verizon's BYOD imei checker and their page brought up a pop up saying it was on the lost/stolen list and to call Verizon's customer service number.

Then we found this thread, thank you all for the tips! Usados https://imeipro.info/  from above and confirmed Verizon had blacklisted our imei numbers. Called Verizon, this time the rep needed not only the 4 digit pin for the deactivated account but also a verbal verification from the account owner (my dad) who we had to get on the line with her. He said yes (they never confirmed identity just apparently needed a different person's voice saying yes) and then she started trying to look up the data. I'll say this, the agent tried really hard while facing a lot of breakage. Apparently accessing closed accounts is very glitchy in their systems for regular customer service. She had to wait on hold for their fraud department and the person she spoke to said they couldn't find the blacklist lock in several lists and they advised me to bring the devices to Apple and have them replace them. These are out of warrently watches so that's ridiculous as it's not even Apple's fault.  I took advice from this thread again and said I have confirmation the lock is on Verizon's side and I'll have to go to the FCC after this if we can't resolve it. Was very nice and extra patient. She went back, tried adding our imei numbers and hit the lock as well. Got another fraud agent and our call was transferred to her. She was able in two minutes to take our numbers off their lost/stolen list and waited while I confirmed on their BYOD website. Whole call was 1hr 5 min with Verizon.  It took so much legwork and customer service calls to figure this out. Hopefully cellular data will work in 72 hrs once the blacklist updates across all the company lists…