The customer service agent has assisted us.

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. The customer service agent that assisted had provided us with excellent customer service. We were impressed by the quickness of his responding back to us, his patient and
  2. The customer service agent who assisted us was very professional. He has provided us with high standard of customer service. We were particularly/especially impressed by the quickness of his response both on email and phone. He possess good product knowledge and he has been very patient and dealt with us affably throughout the whole buying process.
  3. Customer service agent should provide excellent customer service to customer by being friendly, courteous, knowledgable and quickness in responding to inquiry both phone and In-person.

Are the above sentences correct? Please advise.

2

1/2 combined - you can leave out elements:
The customer service agent provided us with excellent service. He displayed a good product knowledge and was very affable and patient. We were particularly impressed by his professionalism and the speed of his responses.

  1. Customer service agents should provide an excellent standard of care by being friendly, courteous, knowledgeable and quick to respond to inquiries both in person and on the phone.