CALL token by GCA is the first ERC777 token.
ERC777 standard defines a new way to interact with a Token Contract. 

This standard was taking advantage of ERC820 which was not in a final status last months. Taking this important point into consideration, we decided to don’t distribute or sell CALL token waiting for final Status of ERC777 and its ERC dependencies.

ERC820 standard defined a universal registry smart contract where any address (contract or regular account) can register which interface it implements and which smart contract is responsible for its implementation.This 820 standard keeps backwards compatibility with EIP-165
Recently, ERC1820 has superseded ERC820 and ERC1820 will be switched as Final Status in the coming weeks.
ERC777 and CALL Token will use final ERC1820 for its implementation.

ERC1820 fixes the incompatibility in the ERC165 logic which was introduced by the Solidity 0.5 update.
You may have a look at the official announcement, and the comments about the bug and the fix.
Apart from this fix, ERC1820 is functionally equivalent to ERC820.

The Smart Contract of CALL token will be soon updated with Final ERC777 and ERC1820. A new Smart Contract for CALL will be redeployed by GCA. Waiting that step, none existing token will be distributed or sold. An announcement will be done in coming weeks when this step will be done. That will be an important Milestone for the project.

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Warmest Regards,
GCA Team