Final answer:
When dealing with customers with language differences, a service provider should use a translator or interpreter to ensure effective communication and understanding.
Step-by-step explanation:
When dealing with customers with language differences, a service provider should use a translator or interpreter. This ensures effective communication and understanding between the service provider and the customer. Speaking louder and slower (option 2) may not always be effective as it can come across as condescending or patronizing. Ignoring the language barrier (option 3) is not a solution and can lead to miscommunication and frustration. Guessing what the customer is saying (option 4) is highly unreliable and can result in misunderstandings.