In an open letter to customers, AT&T has announced they will be increasing Early Termination Fees (ETF) on smartphones and decreasing them slightly on other phones. AT&T will raise the fee from $175 to $325 on contracts for smartphones as well as netbooks. The ETF will be reduced for non-smartphones to $150 from $175.

These changes will only take effect for new and renewing customers. The ETF will be prorated $10 a month for each month ($4 for non-smartphones) that passes in the two year agreement.

AT&T is stating this increase had no relation to any specific phone and instead states the modifications are in response to the overall cost of smartphones that require a larger subsidy.

You can find the complete letter over at AT&T's website.