It seems extremely irresponsible and illogical that a person would choose to break a lease, forfeit a security deposit, spend time looking and applying for a new place, and physically move as opposed to switching their phone carrier.Either this person is BSing about the reason for moving or their problem solving skills are terrible, extremely terrible.

You already said you'd return their security deposit but, since they're breaking their lease, be reminded that you're forfeiting your recourse for them breaking their lease by returning it.

Then I realized I was forfeiting over over $300 a month in interest charges.

Mine says attaching TV equipment to the building is grounds for forfeiting the entire security deposit.

@Roland Paicely Not that I would ever allow it, but If some knucklehead put up a $10 EMD on one of my properties and then defaulted I wouldn't bother forfeiting the deposit.

Best to be at least an agent or better yet a broker so that you can place and monitor your bids and forfeit commissions on the buy.

IF A PET HAS BEEN KEPT ON THE LEASED PREMISES AT ANYTIME DURING THE LEASE, THE DEPOSIT WILL BE FORFEITED

If move-in date is less than two weeks away, $200 Holding Deposit, refundable when they move-in and pay first month's rent/security deposit/move-in fee, forfeited if they do not follow-through. 

Buyer sues on State Court, Seller files bankruptcy and forfeits house to bankruptcy court.

Ignore them and they can and will value your property higher and you forfeited your appeal right.