Verizon Wireless recently multiplied the fees it charges when customers break smartphone contracts by two times, a sudden development which shocked everyone and led to the Federal Communications Commission to demand an explanation from the telecom company for the move.

In November, Verizon surged its fees from $175 to $350 for users who break contracts. Like many of its counterparts, Verizon also offers smartphones for subsidized rates and then hopes to make the redeemed money back through the service fees charged over the period of the contract.

"Smart phones quickly became a major part of our business and cost us a whole lot more", Verizon spokesman Jeffrey Nelson explained.

FCC's letter to Verizon was sent across on Friday, and demands that the carrier explain how customers would know if the increased fees applies to their phones or not, and whether or not has this clause been specifically included in the formal contract agreement. Also under the regulator's scrutiny is the additional $1.99 data access fee which has been included in bills of consumers who do not have data plans but had accidently ended up "initiating data access by hitting a button on their phone".

Verizon has been given a deadline of December 17 to send in its due explanations.