Getting the internet (São Paulo)

I have been 5 times into the TIM shop. Yes, 5 bloody times! Everytime they need something else, and I have given up trying to buy internet services. Seems that they don't want my money.

I have a Brazillian wife, so you'd think we could do it. Anyone got any ideas of the best way to get mobile (not on a cell phone) internet?

Oi company has $70.90 monthly for 10GB, but their modem is very expensive R$199. Any one know of any other company that doesn't treat you like a criminal?

THANK YOU