Answer:
Susana y Sebastián, ¿ Nos llama por teléfono la abuela a ustedes?-- Sí, Nos llama mucho.
Step-by-step explanation:
It would actually make sense if you use -nos because using te would mean
Does your grandmother call you on the phone? - Yes, she calls you a lot. The second part wouldn't be correct. using nos would mean
Does your grandmother call you on the phone? - Yes, she calls us a lot.