Buy WoW Legion in Battle.net Store (pay with direct debit)Activate it, log in, boost your characterNow the trick: if your bank balance is too low for the price of legion or if you let charge it back your Account will be downgraded a few days after and you can´t play with your boosted characterTo play again with your boosted character you need to buy WoW Legion in Battle.net Store again (this time pay with credit card or paypal or directbanking etc.)Now you log in and should be possible to play with your boosted character again (if not => contact GM)So your Account is now fully upgraded and your character is unlocked - but now you got a lv 100 boost in your account available againThis happened to me by accident, I had to contact a GM to unlock my character after i paid the second time, guess the system is not prepared for a case like this to unlock your char automatically.
I hope this guide is understandable, if you have any questions just ask. If a mod/admin think that this is a kind of fraud feel free to delete it asap. (in my eyes it is not)

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