"Casual Access" simply means that the caller is accessing the long distance network without switching long distance companies. (call 10321) Instead, the caller accesses the long distance network "casually", by dialing extra digits which instruct the local phone company which long distance network to which to send the call.

Examples of this dialing sequence for domestic calls utilizing the "Big Three" are;
1010288 + 1 + area code + phone number - AT&T
1010222 + 1 + area code + phone number - MCI
1010333 + 1 + area code + phone number - Sprint

CAUTION - DO NOT use casual access dialing methods unless you have an account already set up with the carrier in question, or else the calls made in this fashion will be billed to you at atrociously high rates.

If you DO already have an account set up, this can be an effective way to reduce your costs. Many people feel uncomfortable swicting their long distance services to some of the smaller less known companies.Casual access enables you to keep your current long distance provider while receiveing the low casual access rates. You might casually access a carrier for  international calls which are less expensive than with your primary carrier.  Or, you might want to take advantage of a special promotion offered by one of the "Big Three", and you realize that to do so, you must remain PIC'd to the carrier offering the promotion (none of the Big Three will honor promotional deals or rates unless your line is PIC'd to them) - so you PIC your line to that carrier and dial most of your normal calls casually with a lower cost carrier.