I have posted in my inital post reply from Steam Support, saying that they cant do anything though..

I saw it - its not a Bungie issue though. Its a problem only Steam can fix as its an issue with their storefront - silver isn't purchased in-game but instead via platform stores. They are misinterpreting it and replying with things such as 'You're welcome to keep trying your purchases in-game' is incorrect. You'll need to keep contacting them for a fix, the issue only seems to have began happening after they applied the sale price on Silver