Halifax refused my PPI claim

[stopthenoise]

Ok, I'll try to keep this short. In 2005 OH and I took out our first mortgage with Nationwide. They told us that now we had a mortgage we HAD to have PPI. Their premiums were too expensive so we went to Halifax where they confirmed, yes we did need PPI now we had a mortgage. Still expensive but as we thought we needed it we took out the policy. Over the years we've paid monthly premiums and kept the policy as a 'just in case'. I got made redundant this year so made a claim for unemployment. As I only worked part time and didn't pay NI, they refused. I went into Halifax when I went part time (3 years ago after having DS) and they told me the policy wouldn't be affected. But it was as I was no longer covered for unemployment. If I had known this at the time I would have cancelled the policy there and then.
So, made a claim for miselling and unsuitability and they have refused.
What now? Surely I have a case?

Go to the Fos, and give them as much detail as possible. They have forms online you can fill in.

What was Halifax's reason for not giving a refund?

I've only spoken to them on the phone and they said the reason was that I was not misold. Even if they decided this I still think they were wrong for not telling me my cover would change 3 years ago. They said a letter was sent out on the 22nd July telling me their decision which is a bit strange cos someone rang me on the afternoon of the 22nd asking for more information as the case was still open so how could they have already made a decision??
I will look on the fos website. thanks