Byju's — unnecessary phone calls

As per their requirement they asked for my contact number for further assistance, and now i keeps on receiving unnecessary phone calls and emails which i find really annoying. Almost 3 to 4 calls i receive daily are from byju. They are envading my privacy which is highly inappropriate.
And earlier i asked them how to delete my account permanently but the steps they told doesn't work on their app. So i asked them not to call me anymore but i guess they are too busy to sell their products. Please sort out my problem.
Thank you