If your phone number's voicemail is forwarded to Google Voice, change your voicemail back to your regular phone number before you delete your Google Voice number.

When you change your number on Telegram, all your chat history, contacts, messages, and media will be moved to your new number. You must enter a verification code sent to your new mobile number.

Consumer Reports tells you how to change your cell phone number and keep your old one, too. It just takes a little planning and some help from Google Voice.