Kukai is a web app that can be used on mobile devices. It is important to be aware that there are scammers out there who may try to impersonate admins by sending private messages. If you have sent XTZ to your Kukai account and have not seen it reflected in your balance, you should contact the Kukai support team for help. They will be able to investigate and resolve the issue for you. It is important to remember to always remain vigilant when using online services and to always double check that you are dealing with legitimate sources.