The scam involves instructing you to add a custom network to their cryptocurrency wallet. This network, as described in your case, doesn't follow the standard specifications of established blockchain networks (e.g., Bitcoin's mainnet or Ethereum's mainnet). The custom network settings (like the RPC URL and Chain ID you mentioned) lead your wallet to interact with a blockchain that is controlled or influenced by the scammers, not the legitimate Bitcoin or Ethereum networks.

The asset labeled "BTC" that appeared in your wallet is likely not real Bitcoin. They control the issuance and transferability of these tokens on their custom blockchain or network, making it seem like you've received actual currency when, in fact, you've received a token with no recognized value outside their controlled environment.

If it were genuine Bitcoin, you would be able to send it to any Bitcoin address without issues. The same goes for legitimate ERC-20 tokens on the Ethereum network; they can be transferred to any Ethereum address, assuming you have enough ETH to cover gas fees.

Do not pay any more fees or follow additional instructions that involve sending money or valuable information to the scammers. Keep a detailed record of all communications, transactions, and steps you've been instructed to take.

Genuine Bitcoin transactions do not require the involvement of custom networks or ERC-20 tokens, as Bitcoin operates on its own blockchain with its distinct protocols and addresses.