If in Phillipines, giffgaff would not be my network of choice. Rates would be:
IF you do not want to run up a large bill, ensure you have any auto top up functions off here https://giffgaff.com/profile/payment-details and if you do not want to continue using your giffgaff sim, remove any stored card details from your account too, using the same link.
After 6 months of non use, your sim will be deactviated, or you can message an agent to ask them to cancel your sim https://support2.giffgaff.com/app/ask/My-account/Cancelling-my-account/form/
Although you can use your giffgaff sim in The Phillipimes @rays8142 you will have to use Airtime Credit as Goodybags only work in the U.K. and (for periods of time) in the E.U. / EEA.
As it will be quite expensive you may need to top up quite regularly.
Note: if you use Auto Top Up this will only work for a maximum of 3 times in any given month so depending on what amount you set as your default Top Up - up to a maximum of £30 - you may need to make top ups manually.
There are no contracts with giffgaff so if you mean that your goodybag renews automatically each month and so you wish to cancel it then this is something you must do yourself.
Go here and make sure that Recurring Goodybag is set to OFF
If however you want to stop using giffgaff altogether again go to the payments page and make sure that both Auto Top Up and Recurring Goodybag are OFF after which remove your card details.
If you have any Airtime Credit left on the account use it up and then just stop using the sim and after 6 months of non-use the sim will deactivate an day the number will be recycled.
If however you want to take your number to a new provider then you will need to follow the advice here
Hope that covers all eventualities!