It's important that your mother has a good-working phone to use on our 4G LTE network at all times. I'd love the opportunity to review your options with you.
You mentioned you previously purchased a 4G LTE phone for her but was unable to activate it. What was the exact model of the device you purchased for her? Also, here's a link to our current Basic Phone devices that will work on our network: http://spr.ly/66071HrQv. Do any of these interests you?