Moiseh,
You haven't said where you are. With over the air internet location is everything. If you are not in a good location you are not going to get very good internet service. We are in Valle de Juarez at Hacienda Contreras and Telcel has always been very poor here - but we get by. You can be in good locations or bad locations. If there nearest towers are not able to get a signal to you or if too many others are using the service then you are just not going to have a good internet experience. This is true of any internet service in the states as well. There can be multitudes of reasons. Land lines and cable provide more stable service. But for those who travel these air cards are our only option. Calling Telcel may help but chances are it is just your location.