"I cooperated with you on a giveaway and you didn't send the prize to the winner. So, how can you contact me again before even sending the prize of the first giveaway? There are many bloggers who complain about your company. Sorry, I cannot work with you until I see that the winner gets her prize. It's been two months!"
They still don't answer me. So, I don't recommend you to enter their giveaways, because I guess you won't receive your prize even if you are the winner.