Explanation
CustomerB reports that the check-in app returned only one search result for their last name, which is not the correct name.
The Filter function finds records in a table that satisfy a formula. Use Filter to find a set of records that match one or more criteria and to discard those that don't.
The LookUp function finds the first record in a table that satisfies a formula. Use LookUp to find a single record that matches one or more criteria.
The Search function finds records in a table that contain a string in one of their columns.
Reference:
https://docs.microsoft.com/en-us/powerapps/maker/canvas-apps/functions/function-filter-lookup