Byju's — receiving unnecessary calls, so annoying

Hi,
Im when i see their ad, I just want to download the app to check what they have.
Later i think i dont need this app, and unistalled it.
after some months, they started to call me daily to buy their monthly plans.
I told them everytime im not intrested bt they calling me again and again.
Even im not yet married, Everytime they asked my children name, Wife name and school name.
How to stop this nonsense?
It is so much annoying.