referntial integrity issue with two tables cant delete a record
You have a foreign key from payment details to customers.

This is a declarative referential integrity constraint which enforces that you can’t have a row in payment details (‘child’ row) for which the customer is is not in customers (‘parent’).

The idea is to maintain data consistency - if you had an ‘orphan’ child row without a ‘parent’ Customer, you would never know which customer made the payment.
If you want to delete the customer and his payments, you can either delete the payments first:

DELETE FROM payment_details where customer_id = 1


Or you can define the foreign key as a cascading one in which case the engine will delete it for you:

CONSTRAINT customer_idfk1 FOREIGN KEY (customer_id)
    REFERENCES customers(customer_id) 
    ON DELETE CASCADE