Official channels, run by Hedera, are found here:

Telegram: https://t.me/hederahashgraph
Discord: https://hedera.com/discord

Also, unofficial channels, run by the Hedera community, are found here:
Hedera Community Chat: https://t.me/hashgraph
HBAR Foundation: https://t.me/hbar_foundation_official

If you are a member of an unofficial chat that is not included above, then please submit a request, including the group's URL, using this form: https://www.hedera.com/contact/