If you start a 30-day Amazon Prime Gaming free trial today, you will be able to claim all 3 transmog helms for free in World of Warcraft.
The following method won’t work for everyone because, in some countries, you only get a 7-day trial Amazon Prime Gaming trial. However, if you can get a 30-day trial, you’ll be able to claim all 3 transmog helms for free, as the third one can be claimed one month from now (starting August 24).
From June 29 – July 26, you can claim Jewel of the Firelord.
From July 27 – August 23, you will be able to claim Hood of Hungering Darkness.
From August 24 – September 20, you can claim Crown of Eternal Winter.