Module "Call me back" does not work after submitting form

[David]

I have a module called "Call me back". This module that adds the option to the customer to leave his/her telephone number so you can call him/her back.

 

The problem is that after submitting the form nothing happens, and after inspecting elements there is an error that says:

 

method=callmebackSubmit&ajax=true&product_id=7&token=0b7297325e5a2ce938706575d423ccba&callmeback_name=David&callmeback_telephone=9999999&callmeback_surname=&callmeback_email=&callmeback_telephone2=&callmeback_hours_from=&callmeback_hours_to=&callmeback_msg=
callmeback.js:69

 

Uncaught ReferenceError: callmeback_ajax is not defined
    at HTMLButtonElement.<anonymous> (callmeback.js:69)
    at HTMLButtonElement.dispatch (jquery-1.11.0.min.js:3)
    at HTMLButtonElement.r.handle (jquery-1.11.0.min.js:3)

 

I'm using Prestashop version 1.6.1.17 .

 

I would like to know how I could find the bug

 

This is the module:

callmeback.zip