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SIM swaps are a huge problem in the wireless industry. Every carrier has had issues with customers having their phone line “swapped” to another SIM card held by an attacker. That attacker then usually logs into financial accounts to drain the victim’s money using two-factor codes sent to that line.

A month ago, T-Mobile disabled self-service SIM swaps while they were “implementing extra security measures around SIM changes”. Since then, customers who wanted to change the SIM assigned to a particular line have had to contact support. During that interaction, support had the customer acquire a verification code either by email or SMS before the swap is completed.

According to documents shared with us here at The T-Mo Report, a new SIM block service has been created to allow customers to put a block on either individual lines or an entire account to prevent the SIM from being changed.

According to the document, store reps and support will have the ability to enable or disable these blocks as requested. When a customer needs a SIM changed, if they have a block active it will need to be disabled before the SIM swap can be completed. The document states that when a block is active, the customer’s account must be verified using a one-time passcode. This is likely via email or SMS to the existing line or another line on the account.

Customers can also access this new SIM block feature themselves either online on the My T-Mobile website or via the T-Mobile app.

Presumably, this means self-serve SIM changes will return soon, but so far it’s still not available. Customers who want to change their SIM card and have the block enabled will likely need to disable the block themselves by providing the website or app a one-time passcode just like if it were done in a store or via support.

It’s unclear why T-Mobile hasn’t decided to have this feature set to ‘On’ by default, given how prevalent the SIM swap fraud issue is. That being said, if you are a T-Mobile postpaid customer, you will probably want to go in and enable this for all lines on your account.

These changes should go live today, December 8th. T-Mobile for Business and customers with more than 50 lines are not currently eligible for this feature.

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