TEHRAN, Jan 10 (Reuters) - Iran's currency has slid 20 percent against the dollar in the last week despite central bank intervention, and Iranians concerned about the economy said on Tuesday attempts to send text messages using the word "dollar" appeared to be blocked.

The central bank reportedly pumped $200 million dollars into the market last Wednesday after new and much tougher U.S. sanctions prompted nervous Iranians to change rials into hard currency, accelerating a rise in the price of dollars on the open market.