For integration testing purposes we have created a dummy carrier for every country. That will allow you test different payment flow scenarios without making any real payments and without needing to have access to any real SIM cards. Sandbox carrier codes always follow a pattern sandbox-xy, xy representing the country code. To test payments in Estonia you could use channel sandbox-ee, for Malaysian payments you could use sandbox-my etc.
|PIN Send||Failure with Fortumo error code XXX on PIN send||***777XXX||N/A|
|PIN Verification||Failure with Fortumo error code XXX on PIN verification||any||8XXX|
|Charge||Failure with Fortumo error code XXX on charge||any||0XXX|
For example, if you would like to test charging error 701 then you would need to enter 0701 as the PIN code and Fortumo will respond with ERR_701.
For doing live tests with different carriers there is a site called simtest.it which you can use to book different sim cards online.