what can an hourly medical employee be asked to do in Texas?

I have a relative that works at botox clinic, and they pay an hourly wage. They require that the employees answer their phones when a customer calls after hours (its an app with the clinic phone number that has the employees personal phone ring when called). They do not pay extra or outside the hourly wage for this. Also, they do not pay overtime for hours over 40, they just pay the same hourly wage. Is any of this legal? Asking for a relative