(Newbie) with council tax rebanding query - pls help me !

Hello , having been looking at this site for some time now , ive decided its time for action !
PLS bear with me !
You look like a friendly bunch here , so heres my first plea for help !
Ok I have read the article about Council Tax rebanding after seeing Martin on TV some time ago now & am sure Im paying too much CT.

I have checked the VOA web site & my property is an E band , then I checked the house prices on my estate - this is where Im confused , because I live in an Housing Association property, so Im unable to check the price of any houses sold in my road , so I looked for houses around my estate which may have been sold . Now it looks like a couple were sold a while back , and according to that search Im IN the right band , BUT 2 houses in that road have had their CT rebanding changed from an E band to a D band , plus a friend of mine in another road on my estate are a D band also.
which is making me think im in the wrong band.

So my question IS ( sorry its taken so long 2 explain ! ) , does any one think I have the grounds to challange my banding ?
And do I ring the VOA first or do I write a letter ?

I do hope Ive expained this right - pls can anyone help me here

Thank you for reading