Error #1241 - Operand should contain 1 column(s) in Mysql

I just try following query:

SELECT *, 
      (
       SELECT count(*) 
       FROM users 
       where users.email=calls.email
      ) as ureg, 
      (
       SELECT sum(qty) 
       FROM product 
       where product.owner in 
          (SELECT * 
           from users 
           where users.email=calls.email)
      ) as pop 
FROM calls 
order by calls.data desc 
LIMIT 0,20

but I get following error :

#1241 - Operand should contain 1 column(s)

How should I fix my query?

Edit: by changing SELECT * from users where users.email=calls.email to SELECT id from users where users.email=calls.email

it works because the query searches for product.owner in bunch of ids that exist in users

where product.owner in (SELECT *

product.owner is one column, so the subquery should return one column (whatever corresponds to product.owner).