Sen. Maggie Hassan (D-N.H.) alleges that Trump Mobile failed to secure required authorizations for its international calling service and did not submit a complete plan to combat robocalls. The senator wrote in a letter to the company that these oversights raise significant concerns about the security of the mobile service. The letter highlights a recent report that hackers stole personal data from 3,615 Trump Mobile customers. This incident follows a previous confirmation by the company that a vendor it uses exposed customer personal data on the Internet. Hassan points to Trump Mobile's key business partner, Liberty Mobile Wireless, which did file a robocall database but left it incomplete according to the senator's account. The letter asserts that Trump Mobile failed to follow multiple Federal Communications Commission filing rules designed to ensure the security of mobile services.