Unearned Revenue Scenario When Customer No Longs Want the Service

Hi,

We are in R12. I have a scenario in AR where the company agrees to provide a service to a customer for 12 months. Say its Jan 2015 & at the start accounting entry must be

Accounting Entry 1

Dr  Receivables            1200

Cr  Unearned Revenue  1200

At the end of January following accounting entry must be created

Accounting Entry 2

Dr  Unearned Revenue    100

Cr  Revenue                   100

Continuing for February month also above accounting entry must be created. But after February(2nd month) customer no longer wants the service from the company. Therefore

Accounting Entry 3

Dr  Unearned Revenue    1000

Cr  Receivables              1000

How do I set up AR for the above scenario?