Sir while registering it keeps telling me user already exists even when trying with different email address
You're only allowed to register one account per IP address. It's a good way to keep unethical spams. So, try a different device if it keeps saying email address already used.
So i can't refer to my co-workers?
No, probably not. I sent my referral link to my coworker and he kept receiving errors. I know we have different IP addresses, but I guess because we are on the same network, it will not work. It's a shame though because I don't know others invested in crypto.