When you add the pass partway through a bill cycle, you are charged pro-rata for those days.
When you remove the pass partway through a bill cycle, you are charged until the end of that period.
Depending how your bill cycle falls, you should compare costs with paying the £2.29 daily charge for the days you use your phone. Remember to also text ROAMING to 150 before leaving the UK - regardless of which billing option you choose, this will ensure your phone can connect to Greek networks.
