Rent random spike

I have been trying to move for 1 month and every time I do my paperwork they raise the rent from the original price. Is that even legal. I have offer to pay on spot to secure the price and always come with you have to fill up paper work and bla bla, and then last minute they raised the price 300-500 in some cases. And when I confront them they say: Our prices change daily. But they dont let me pay or do anytging until I fill up the paper work, and dont honor the price even showing them prices.

Already had the experience with: Memorial Towers add:1,100 in person:1700 Le Parc at Galeria add:1200 in person:1634 33 Weslayan add:1345 inperson:1500 230 W Alabama add:975 in person:1250 510 Post add:1867 in person:2345

Any goverment office that works with this?