If someone clicks "I choose to mail payment" how can I redirect them to the Thank You message and not to Paypal?

My form has the option to buy products through Paypal or to mail in a payment. If someone chooses to mail their payment, I do not want them to be directed to the Paypal site. How can I create a condition so that it takes them to the Thank you page/message? Here is the form:

Also, 2 of the products use Promo codes/Coupons so I can't separate them like I did on this form:

You can achieve it through the condition.

E.g. If "payment method" is equal to mail, hide PayPal field.

This way, when the form is submitted, it won't redirect to Paypal.

Here's a full instruction:

http://www.jotform.com/help/120-How-to-set-up-paypal-along-with-other-payment-options

I followed the instructions provided and it still takes me to Paypal if Mail a Check is selected and I click Submit.

I have reviewed your form and I have noticed you are displaying the products using the payment field:

Please, do note that your form is redirecting to PayPal since the payment field is filled, if your users select at least one product then they will be redirected to the PayPal payment page and, unfortunately, there is not a way to avoid it. 

If you would like to allow your users to pay using different methods, you would need to split your products using basic fields, perform calculations to get the total amount and use conditions to apply the coupon codes. 

Here are some guides that will help you doing so: 

https://www.jotform.com/help/259-How-to-Perform-Form-Calculation-Using-a-Widget

https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

https://www.jotform.com/help/268-Conditional-Logic-Inserts-Text-Calculation-Into-A-Field 

I hope this helps.