On Samsung Galaxy S devices and other Android phones, you can add multiple phone numbers to a contact and add following tags to them: Home, Work, Mobile, Fax and Custom. In order to do so, do as follows:
1. Open "Contacts" App and Tap on the person you would like to add more phones to
4. There you can add another phone number and assign a tag to it
5. After adding the new numbers, tap on Save and you are done.