[Resolved]  Byju's — hardware/software issue

The byju's online classes is not responding to my continuous complain about their defective app loaded tab which is not working. The tab was sent to me with class 6 sdcard in it and no class 7 app which they say will be sent to me next year. Which i find weird since they are having the money for both the classes in advance then why they are holding up the sd card for class 7.
Tab + sd crad was sent to my with payment mode as cash on delivery but on invoice it is written prepaid which makes the thing more weird and doubtful though i still have the invoice but there is no mention of byju's classes on it. The only proof i have is their sd card. Please help me to get back at least half of the money of class 7. I dont want to continue with their classes.