The first step in exerting control over magazine supply to your newsagency is to advise the magazine distributors of the total pockets available. Putting this in writing to them provides them with information the most likely do not have today. It establishes your land mass, thereby providing them with the information necessary to not over supply you.
While the magazine distributors do not work together on equitable ranging – stupid as that is – them knowing your total number of pockets and their own knowledge of the titles their computer carries means that they should behave more fairly toward you.
Write to the distributors, let them know your pockets and send this in an express post envelope or as registered post – so you can prove the received it.
You should send this letter any time you change the amount of space you allocate to magazines.