Well, you can't have 2 on the SAME phone line, but you COULD get a SECOND phone line with a secondary ISP on that line (provided there is another DSL service in the area, and also that you are 18 years old to be able to order it).
If you do this, when you call the telco for the 2nd line, request just a CORE LINE, no long distance or caller ID or call waiting for 'fancy fluff', just the line THATS IT, it will be a little cheaper.... Also, depending on your distance from the serving CO, or neighborhood gateway, it is possible that the service will be about the same as your current ISP. Is there cable available in your area?