Count the payments per customer.
select t2.first_name, t2.last_name, count(t1.amount_payment) from customer_payments as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t2.customer_id
Just for those with more than 2 payments.
select t2.first_name, t2.last_name from customer_payments as t1 join customers as t2 on t1.customer_id = t2.customer_id group by t1.customer_id having count(*) > 2;