I got Minecraft for 20.95 from MMOGA and received a code.
I redeemed this at Minecraft.net under Redeem and then only had to set a player day. When I start the launcher it wants a mojang or microsoft account. But I haven't created one anywhere. At MMOGA it said that I also get premium. When I start the launcher, it only says that I can play the demo and please buy the game to unlock everything.
When you redeemed your code you probably had to enter your code and an email and also a password… Try the login data from there. As far as I have seen, you have to register with Microsoft to redeem it, test it out in the launcher… For next time (if you get a 2nd account or something), create an account beforehand.
Seems like you got pulled… Minecraft doesn't even have a premium feature…
At most in the Bedrock the Starter Edition