How to check:
Open your chat with the person.
Tap on their profile picture/name at the very top of the chat to open their profile.
If their phone number is public, it will be displayed on their profile page, usually below their name or username. You can then tap on it to call, copy, or save.
If They Are in Your Phone's Contacts AND telegram number database Their Privacy Allows "My Contacts":
Scenario: You have their phone number saved in your device's address book, and they have set their "Who can see my phone number?" privacy setting to "My Contacts" or "Everybody."
How it works: Telegram will automatically match the number in your phone's contacts to their Telegram account, and their name (from your phonebook) will appear in Telegram. If their privacy settings allow, their number will also be visible on their Telegram profile.
If They Explicitly Share Their Contact with You:
Scenario: In a chat, a user can choose to directly share their contact card with you.
How it works: They tap the "paperclip" icon (attachment menu), then select "Contact," and choose their own contact card to send it to you. This is a deliberate action on their part.
When You CANNOT Get a Phone Number (and Why):
From a Telegram ID/Username Directly (via Bots or Third-Party Tools):
Reason: Telegram's Bot API and the platform itself are designed with privacy in mind. There is no legitimate, built-in way for a bot or any third-party tool to retrieve a user's phone number just from their Telegram ID or username without their explicit consent.
Warning: Be extremely wary of any "tools" or "bots" that claim they can do this. They are often scams, phishing attempts, or could compromise your own account. Telegram actively prohibits such unauthorized access.