[entwisi]

Nope, your reading is incorrect, the comma defines it the statement by the final operator i.e. OR

Will I be charged for banking with first direct?
Provided you credit your Bank Account or Cheque Account with at least £1,500 each month (internal transfers from first direct accounts excluded), keep an average monthly balance in excess of £1,500 OR have an additional product (see next question for details) with first direct you will not incur our banking fee.