Tap the Edit icon (upper-right).
If prompted, select the contact source to edit.
Depending upon the account type, the options presented may vary.
Edit any of the information (e.g., phone, address, email, etc.) then tap Save (in the upper-right).
To add a pause (a 2-second delay between numbers) or wait, tap *#, tap 'Pause' or 'Wait' then tap Save.
Tap More fields (lower left) for additional contact fields (e.g., Website, Date, Relationship, etc.).
To change the type of a selection (e.g., Phone, Address, Date, etc.) tap the Dropdown menu then select the desired choice (e.g., Mobile, Work, Birthday, etc.).