Byju's — I want to cancel my order to byju's

I was purchased the product 15 days back (dtd 25 oct 18), and one product having issue to open the same. which is not rectify till 27 oct 18, and another is also having some issue. the customer helpline no. provided to me was not ok. it go through IVR OPTION WHICH ARE NOT PROPER. so that I could not connect to mentor of byjus till date. but on today 15/11/2018 I contacted to cancel the order, they say you have inform me after 15 days. while it is not working 5 - 10 days properly. I send the mail for byjus support team for refunding the amount but one of the person Harshit Dwivedi. contact but she told refund is not possible because already 15 days is over but i don't want to go to pay emi. Now i don't want above product because no body will responding. They are cheater. Please cancelled the application and refund the amount.