My mom got a budget Xiaomi (Redmi 9A), but she's having problems with connectivity during calls in places where other phones work fine, like her apartment. Also

My mom got a budget Xiaomi (Redmi 9A), but she's having problems with connectivity during calls in places where other phones work fine, like her apartment. Also, currently she's abroad and call connectivity is horrible for first 15-30 seconds, then the call drops and after redialing it works fine. Really weird. Probably should exchange it for a new one.