T-Mobile US Inc. will fire corporate employees who are not fully vaccinated against COVID-19 by April 2, according to a memo to staff obtained by Bloomberg News.

In the email to U.S. employees, the wireless carrier’s human resources chief also said that office employees who haven’t received the first dose of a vaccine by Feb. 21 will be placed on unpaid leave. The policy applies to all employees who need “regular or occasional” access to T-Mobile’s offices, which the company says includes almost all staff.

“Affected employees who do not become fully vaccinated and obtain a Magenta Pass by April 2 will be separated from T-Mobile,” Deeanne King, T-Mobile’s chief human resources officer, said in the memo, referring to the internal digital pass that requires the proof of vaccination.

Exemptions will be made for medical and religious reasons, she said.

In a statement, T-Mobile confirmed its vaccination deadline for office staff.

“T-Mobile’s badge-controlled offices continue to be accessible only to those who are vaccinated against Covid-19 and we have shared with employees that we are requiring office workers to be fully vaccinated by April 2,” it said, with limited exceptions for certain roles, locations and legally mandated accommodations and exemptions.

The memo stated that the rules will be slightly different from those in customer service centers to “avoid impact to customer experience.” Instead, support employees will still have to show proof of the first dose of a vaccine by Feb. 21, but they will not be placed on unpaid leave.

Proof of full vaccination will still be required by April 2, however, which is when T-Mobile told staff it intends to bring all representatives back to on-site or hybrid work environments.

The vaccine rules and decision to terminate unvaccinated employees won’t apply to field technicians and most in-store retail roles, the memo said. The company is however encouraging the shots and regular testing for those workers.

“While we hope every affected employee will be vaccinated and return to their workplace, we understand that for some, this means you must make a deeply personal decision,” King wrote. “Uniting around this plan helps us all move forward with greater clarity and safety for out community.”

T-Mobile isn’t the first company to mandate vaccines, but it is one of the biggest firms to tell staff that they will be terminated if they do not receive the shot. Other companies, like American Express, told staff they’d have to work remote if they don’t get vaccinated.

Last week, the Biden administration withdrew plans to require certain large businesses to mandate Covid vaccines.