The OP wants to do the VLOOKUP based on the customer name, so to use VLOOKUP, the customer name and account number columns need to be reversed in the data table so theat the lookup column (customer) is leftmost. The AccountView tab could be enhanced with a drop-down box for the customer name using a data validation list that refers to the customer column on the Data tab.
For the OP's benefit:
What a VLOOKUP query does is match the lookup value in the leftmost column of the array given in the formula, then looks across to the column stated and returns that result.
=VLOOKUP(lookup_value, lookup_array, column_number_in_array, true/false) where false returns an exact match and true returns an approximate match.
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