Did you try the suggestion above? Swapping sims with your wife and seeing if it's a Sim or Hardware issue? I had this issue before and it was resolved only after resetting my phone back to default. Hope this is not the case for you.
Hope this helps: Public Mobile 3G Frequencies850 MHz, Band 5 (UMTS/ HSPA)1900MHz, Band 2 (UMTS/ HSPA)Public Mobile 4G Frequencies1700/ 2100 MHz AWS, Band 4 (LTE/ LTE Advanced)700 MHz A/B/C/E, Band 12/13/17/29 (LTE/ LTE Advanced)
