Had a return customer create a new user account with identical details (including email address), with the addition of a company name on the new account. Is there any way to:

1. Restrict customer creation to one customer per address

2. Merge the customers so their order history is in one location?

I am new to ZenCart, so apologies if this is something very simple. So far, so good, although I haven't been able to get PayPal Pro working for credit cart payments as of yet, but I haven't put a lot of time into that.