How To Cancel a Policy Where First Premium Was Never Paid?

back in November 2014 I was laid off, I was concerned because I was facing no health care coverage. I went on line and with the assistance of a health care obama care worker I was able to sign up and at that point it was supposed to go into effect on 4-1-2015. In December my wife’s employer started offering benefits. We were able to enroll with her employer and our insurance went into effect immediately 1-1-15. No initial payment was ever made on the Obama plan due to our fortunate timing of my wife’s plan. I tried on numerous occasions to cancel what I have put into motion in November 2014 but have been unsuccessful. In fact even today I received another call asking me why we have never made a payment. I explained but she said he wasn’t able to cancel my on line Obama application. Can you help me?