You need to send the admins proof that the account is indeed yours, by sending over a signed message[1] of the address associated with your locked account.

Read more: https://bitcointalk.org/index.php?topic=497545.0

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[1] https://medium.com/@TenX/mycelium-how-to-sign-a-message-with-a-bitcoin-address-87afdd0a5a0e