No service

BrucePa_3658090​ We don't know either from what you have told us.

Have you checked your Account dashboard to check that your number and plan are showing as expected?

Are your phone settings checked and correct?

Are you both in the same place i.e. same mast? Have you completed a Network Status check?

Does her sim work in your phone?

Lots of things to check first and then state in your post so that people may be able to help if they know what you've already tried.