1.6 Dormant Accounts
1.6.1 It is recorded that the provisions of this Clause 1.6 only apply if a Players account at the Sportsbook constitutes a Dormant Account.
1.6.2 An Account Management fee of £2.00 / €3.00 / $5.00 per month will be debited from any account that is dormant.
1.6.3 Any credit balance standing to a Dormant Players credit in his or her Cash balance in his or her Dormant Account, less any Account Management fees charged, will be refunded to the Player providing that the player claims his or her Cash Balance from the Sportsbook within six (6) months of the Players account becoming a Dormant Account. If the Cash Balance in a Dormant Account remains unclaimed for a period of six (6) months, any sums contained therein shall be forfeited to the Sportsbook.
http://www.canbet.com/help/sportsbook_general_terms.aspx
They say they're "committed to providing world-class Customer Service, and to dealing with player queries and disputes in a prompt, efficient, and fair manner" so you might still get some joy from them. If you don't, escalate your complaint to IBAS although what they've done, unfair as it is, seems to be within their rules.
http://www.canbet.com/aboutus/complaints.aspx