According to The T-Mo Report T-Mobile is planning on charging a $35 connection/activation fee for most device connections to the T-Mobile network whether you do this online or with a representative assisting you.
Whether you’re connecting a new device to the network, ordering internet for your house, or sneezing into the wind, T-Mobile will channel Sprint and charge you $35 for the pleasure.
Once again, this is with or without human interaction.
There are a few exceptions listed such as customers getting a replacement device, swapping bad SIMs, etc.
According to the source, the new plan fees start on November 15, 2022.[T-Mo Report]