if someone agrees to an agreement through a text messege. is it a legal agreement?

If the agreement is legal, it doesn't become illegal because it was entered into by text message.  If i understand you correctly, you paid somebody to do something which was not illegal, they took the money, but haven't performed the agreement.  You can sue them for your money back or the amount of money you had to pay someone else to perform what the first party was supposed to do.  However, you can't compel them to specifically perform - a Court may order the breaching party to pay damages, but won't order them to perform a personal services contract.