Trump Mobile apparently failed to obtain necessary authorizations to operate the international calling portion of its phone service, Sen. Maggie Hassan (D-N.H.) wrote in a letter to the company today.

Her letter said Trump Mobile also doesn’t appear to have submitted a required plan for fighting robocalls. Trump Mobile’s key business partner, Liberty Mobile Wireless, did make a robocall database filing, but it was not complete, Hassan said.

Hassan’s letter raised questions about Trump Mobile’s security related to a report that hackers stole personal data of 3,615 customers and Trump Mobile’s previous confirmation that a vendor it uses exposed customers’ personal data on the Internet. Hassan alleged that Trump Mobile failed to follow multiple FCC filing rules that are supposed to help ensure the security of mobile services.

“The apparent absence of authorization for Trump Mobile international services raises questions about who is providing or reselling the international telecommunications services advertised by Trump Mobile, the authority under which those services are being provided, and the company’s commitment to complying with requirements designed to safeguard national security,” Hassan told Trump Mobile CEO Patrick O’Brien.

Referring to the recent data breach, Hassan said it’s worrisome that a ransomware group “claimed that when it notified Trump Mobile of the breach, the company responded that ‘[w]e have no team to handle this.’” Trump Mobile also seems to lack a robust customer authentication process and offers “streamlined service activation that can make it easier for scammers to obtain US numbers,” Hassan wrote.

Trump Mobile, which has a trademark and name licensing deal with the Trump family, advertises that its customers can call more than 230 countries and territories. “Yet a search of the FCC’s International Communications Filing System suggests that Trump Mobile does not hold the necessary authorization for these services under Section 214 of the Communications Act of 1934,” wrote Hassan, the top Democrat on the US Congress Joint Economic Committee.