Any reccommendations on some device that works like a prepaid mobile phone but is basically a panic button to call a pre recorded number?

I'm volunteering with a NGO in Mexico and one of our elders, who has very little mobility in her hands and lives on her own, really needs something like that in case she needs help. Usual mobiles for seniors are not suitable (too many keys and too complicated for her) and we can't get her a phone landline at the moment so something like what I described would be perfect for her, problem is there is very little available in terms of products for seniors here and I'm very new at working with elders so I'm pretty clueless about what options are out there, googling around I'm mostly finding services with a monthly fee, but that would not work in Mexico and even if it did I don't think we could afford it long term at the moment. Thank you.