You want to group the data by something like Customer ID (or name) first.
Then, you want to use ‘Work with NA’ / ‘Fill NA with Previous / Next Row’.
If the order inside the group is not what you expect, then you want to ‘Sort’ the data before doing the ‘Work with NA’.
After it’s done, don’t forget to ‘Ungroup’ , otherwise any subsequent operations will be driven by the group setting.
After you fill the NA, then you can remove the duplicated rows!