Username cant be used even thought its free and its taken on mojang website!

What I expected to happen was...:
I changed my name to YellowTehMinerz and after the 30 days I changed it back to Yellowman3108 and it would change

What actually happened was...:
But it didnt change and it then proceed to make every name with Yellowman in it in that sequence unavailable even though they weren't taken.I also got a like 3 or 4 friends to test if they could find any Yellowman name that were free they failed.I also claimed it during the time where only i can claim it because I dropped it.

Steps to Reproduce:
1. Go to the mojang website
2. Try to change name to anything with 'Yellowman' in it in that order
3. Doesnt Change