Your Account
Official telegram.org Source
You can change your number in Telegram and keepeverything, including all your contacts, messages, and media from the Telegram cloud, as well as all your Secret Chats on all devices.
To change your number, go to Settings, then tap on your phone number (just above the username), then 'Change Number'. If you already have a different Telegram account on the target number, you'll need todeletethat account first.
Official Telegram Reference: https://telegram.org/faq
Part of the TGWAY.com Official Telegram Knowledge Base (98 Verified Q&As).