Yes You Can, AppleCare wouldn't be the best contact, although they may help answer questions. Go to www.icloud.com and select find my iPhone, from their you can select "Lost Mode" on your iPad locking your device and flagging it as stolen. Hope this helps https://support.apple.com/kb/ph2700?locale=en_US
Contact Apple customer service they should be able to either disable your service and maybe change your password
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