Final answer:
The appropriate method to address a non-paying customer is to take them to small claims court, thereby adhering to legal processes and avoiding potential violations of privacy or harassment laws.
Step-by-step explanation:
When dealing with a deadbeat customer who hasn't paid his service bill, the recommended and legal approach is option A: Take him/her to small claims court. This process involves filing a claim to seek the court's assistance to collect the debt. In contrast, options B, C, and D could potentially violate privacy laws or result in charges of harassment or theft. It's crucial to follow legal procedures when attempting to recoup a debt to avoid any liability that may arise from improper debt collection practices.