What if you don't ever talk to them on the phone, or go to their office or location? You only communicate with them by sending them emails.
Is Paypal a good source then?
Also, if you charge them a monthly recurring fee is Paypal still a good source? I feel PayPal may not be a good source because if a customer dislikes the services you have provided, or gets angry with you for any reason they can dispute payment and get their money back.
What do you recommend or and how are you guys getting paid?
Post this in the Offline Marketing section.