ETF at T-Mobile USA: Urgent Question!

Hey guys,

I've never purchased an contract phone, so this is all new to me. I have a question regarding Early Termination. I understand that T-Mobile has a $200 ETF. If I were, for example, to purchase a refurbished SGS2 for about $30 on T-Mobile, kept it for a month, and then paid the $200 ETF, would I have to return the phone as well?