Byju's — Cancel My childs subscription please

I have purchased the subscription on trial period on 26th june 2022 as my sister was not able to study BYJU’S course I requested the company to cancel the subscription but I have mailed them countless times and called them too I have only recieved a call from senior manager once and now I have been mailing them and calling them countless times all they say that you will recieve a call from senior manager at the end of the day as I have requested to cancel the subscription within 15 days so please cancel my sister’s subscription