Customers Receive Error Message

I checked your account and noticed that you had not connected the payment integration. You should enter your PayPal and connect it with the form.

In order to setup PayPal Standard, you can check and follow this walkthrough:

https://www.jotform.com/help/391-How-to-Integrate-Form-with-Paypal-Standard-

Then after you configure the integration, I would recommend you to test it. There are two ways to test the payment integration. You can use the Sandbox mode or make a very small payment ($0.01). Here is the guide:
https://www.jotform.com/help/390-How-to-Test-your-PayPal-Payment-Form

Please connect the payment integration and test again and let us know, if it helps.

We will wait for your response.

I use Square. Do I have to have a PalPay account to use this form?
...

Is there a way for me to “not connect” the form so that I can just process
payment via phone calls?
...

The Single Product Multiple Choice Orders form on your account Occqpie has a PayPal Standard payment field. If you want to use Square, remove the PayPal payment field and add the Square payment field. 

How to Integrate Form with Square

If you want to collect payments via phone, you can use the Purchase Order payment field.

How to Create Payment Form with Purchase Order