Need help porting to ST

[Wing123]

Hi, I am having trouble porting my number from AT&T prepaid to ST(Verizon sim card) today. The phone I have is Galaxy Note 8 originally from Xfinity Mobile but its unlocked so it can be used on any carrier. I am using it on AT&T with no issues. However, the representative told me the porting cannot be completed because the IMEI is active on another network. I have two questions:
1. Does a phone's imei have to be whitelisted by ST/Verizon in order to be used on the ST?
2. I have a cheap phone LG 329G bought from ST when I purchased the 6 months service. Can I use this imei to finish the porting/activate the Verizon sim and switch the sim back to my galaxy note 8 to use?
Thanks in advance.

[Wing123]

Anyone? I never had issues porting with any other carriers. This is frustrating...

[ST - Mark]

Hi Wing123. My name is Straight Talk Mark. Sorry that you’re having a problem. I will contact you directly with a private message. Thanks.