I’m relatively new to SAP (December last year), so forgive me if I’m out of my depth and missing this question’s point altogether, but it sounds as if the question is “why is the telephone number only showing for some customers?”. If you run transaction XD03 you will be able to view the customer master record for that customer, and you may find that only some of your customers are maintained with a telephone number. As this data is only pulled across from the customer master record, if this information is missing it will not have a telephone number to correlate with the order. I hope this helps, and apologies again if I’ve missed the point of your question!
All the best,
Cardiff County Council System Administrator
(Former trainer for Recurring/Periodic Billing)