How do I deactivate 'find my iPhone' if it has been water damaged and I need to send it for repair

MY iPhone 5 has been water damaged and I need to send it for repair. I have been asked to deactivate the 'find my iPhone' setting or they may not be able to complete the repair. I have tried to access my iCloud account to locate my devices to carry out this instruction, but haven't been able to locate my device to deactivate it, is this because it is not visible on the network?