Look into iDSL. ISDN is generally a per minute charge plus extra cost for ISP stuff. iDSL is using same technology (as ISDN, same speeds, etc) but usually unlimited. DSL Reports has price comparisons. There are also forums there with users who can talk about both (I haven't used either but did shop prices).
IIRC iDSL Price was $69/mo + some fixed charge for a year contract, usually comes out to $99/mo.
Also, see if there are any Wireless ISP's at the same website (wireless, not satellite though, sat = last resort).
DSLReports ISDN forum