Season Ticket Discount - Oyster.

According to

If your season ticket is on an Oyster card, SWR will consider an Oyster/Travelcard if:

• You bought a Travelcard (either a ‘paper’ ticket or Oyster card) from somewhere other than South Western Railway. But we will consider your claim if you have proof that you use our trains for all, or part, of your journey – such as a home or work address close to a station we serve, and details of the journey you make

I live in Wimbledon and travel to/from Waterloo, 5 days a week.

However it then says to claim:
• If you bought your ticket elsewhere please apply in writing to our Customer Service Centre and enclose your expired tickets.

How is this meant to work? I can't post my expired ticket and then wait for a new one to be issued, what I am supposed to do in the meantime ?

Thanks, Daniel