*67, when dialed before a phone number, will suppress your number from appearing in Caller ID on the recipients phone.
Note that this is carrier dependent. Most carriers support this, but not all. Your number can NOT be hidden in this way when calling any toll free number (800, 877, etc) or when calling government agencies such as the police or fire department.
*69 will dial the number of the last party to call you so long as they did not block caller ID and the number reported is valid.
This is also carrier dependent. it’s rather pointless today as you can dial the last number that called you by tapping on the last call in your call log.