I think you need two tables.
Table 1: you input the info you take over the phone, each item gets its own field of course. Then there’s one extra field with some sort of unique ID (could be an autonumber to keep it simple).
Table 2: One linked field to that unique ID from Table 1, and fields for the remaining data you need to collect. Make a form of Table 2 and send people the link to the form with the unique ID field pre-filled. {link to form} followed by “?prefill_” followed by {the exact name of the unique ID link field in Tabled 2, not Table 1; replace spaces with “+”} followed by “=” followed by {the exact Unique ID for that customer; replace any spaces with “+”}
Go back to Table 1 and add lookup fields of the additional data you collect for Table 2.
