Is she cheating?

by Ron
(Canada)

My wife went on a Hawaiian cruise with her 3 sisters. She has been gone for over a week and I have only heard from her once in an email.

In the email she said she hadn't called home because, it costs too much, it is almost impossible to find a pay phone, and beacuse of the time difference if she did find a pay phone it was too stressful to know it was a good time to call.

I feel she is lying to me and that ther may be more going on than she wants me to know.

I would appreciate some advice on this please.
Am I just jumping to conclusions or does it sound like she is being unfaithful?