I buy monthly oyster cards which gives me zone 1-6 train and tube travel for work, which i use every day. I've just found out though that i will be working off site for a month so will only be in london one day during the working week. I've just renewed my oyster card last week and it costs over £180. Does anyone know if i can get a refund or have the card funds 'frozen' so that i can use it when i'm back. Otherwise i've lost quite a bit of pocket change!