Purchased older model phone on eBay + new mini SIM. Att cannot activate new SIM??

I purchased an ”unlocked” phone on ebay + a new mini sim card on ebay. both arrived. i put the new sim card in. i then went to att.com and tried to activeate the new sim card. each time i keep getting an error message. i called att and they were not able to help me. they said every time they try to activate the new sim card with this phone, they get an error. on the phone, it says sim card not provisioned mm # 2. says emergency calls only.

i dont undertsnad why, when i’ve follwed all the instructions perfectly, that this sim card cannnot be activiated in this unlocked phone. the sim card is installed correctly. it is the correct type for the phone.

this is the phone i purchased:

https://www.ebay.com/itm/Pantech-Link-P7040-AT-T-GSM-Unlocked-QWERTY-Keyboard-Phone-G

this is the sim card i purchased:

2FF-GSM-4GLTE-NEW-Genuine-OEM-Prepaid-or-Postpaid/193390187523?ssPageName=STRK%3AME

when i go into the phone information on the new phone, under My Number, the last number the phone had is still showing and theres no way for me to edit it.i’ve never done this before and do not know what im missing. the att staff overseas is not helpful at all.

is it possible this phone is not unlocked as advertised or the sim card is in fact locked in some way?

any help would be tremendously appreciated as my old phone, a smart phone, is cracked and i can barely see on the sceen to use it. this is why i went back to an old qwerty keyboard style. i cant go into a store for help as they’re all closed due to the covid virus.

thanks so much!

Linda