Past simple/past continuous

Hello,

I used past continuous in the second sentence as I think using past simple would be wrong, am I right?
James Ellis went on a business trip last week. He was visiting some customers in Frankfurt. He left home early on Monday morning and took a taxi to the airport. He got there at about 8 o'clock. He checked in and went to the airport lounge. He bought a newspaper and went to get a coffee.
He was drinking his coffee when he saw an old friend, Bob. He was very surprised that Bob was in London and found out that he was starting a new job in the city. As they were speaking they heard an announcement. "Would all passengers for the 9.30 flight to Frankfurt please go to boarding gate 10". James said goodbye to Bob and as they were leaving Bob gave him his business card and asked him to phone when he returned (return) from Frankfurt.

Thanks