You did not say that you would phone them so you should not collect a phone number. On a payment form, you require the name, address, city, payment information, etc. This is the bare minimum. You do not need their place of work, their interests, etc. because these things are not what is required to complete the job. Another fatal sin of forms is to make a form that is complicated.
Users are unlikely to use forms that are difficult to use.
A difficult form does not have to be a long form as a short forms can also be confusing. However, the longer the form the more likely the potential for errors through complication. A variety of forms are used that require the User to complete different fields in different ways. This is not the problem. The issue arises when different types of fields are intermingled.