Whats link multiple msisdns mean

Yesterday my wife's phone lost its ability to send texts...people were not getting them.  Then strangers started sending texts as if responding to a job offer for a secret shopper...that they got from her phone number.  Like 10+ texts every hour. 

Today she went to the T-Mobile store to try and fix it, and they ended up selling her a new phone.  After the store took care of the new phone and data transfer, she is STILL getting these messages.  The employee at the store said it's called spoofing, and there is nothing anyone can do about it, but the messages should stop in a month.  ¿Qué demonios?

I looked on our family plan T-Mobile activity and found this listed in the Activity section which posted at the same date and time as when all this stuff started happening:

Vincular un MSISDN

Also, my wife's line had a different name.  Everyone's line has the person's name, but now hers is called MY PEEPER.  

It looks like someone haccked into my online account, linked their nefarious phone with my wife's phone number, and re-named her phone line.  Then started sending out their bogus ads to random people.  

Are we just supposed to let this go on?  Is there nothing T-Mobile can do to remove this junk or sever their connection to my account?