Telmex does offer packages with higher speeds but beware of the fine print which says "up to 10 Mbps" or something similar. I have found that replacing the equipment (modems which are always refurbished garbage) provided by Telmex has increased my speed. Ensuring that my telephone wiring is in good shape has also improved my speed. Only after exhausting these two remedies would I then opt for a higher package through Telmex.
I have had TelMex service for 10 years now and I have only received brand new equipment. I have never been offered refurbished garbage.
Just because it looks new and has a sticker does not make it new. Ask any of the Telmex technicians/installers driving around why your speed is not what it should be and you will get the same answer.
Did a quick Google search and saw that others in the Guadalajara/Lake Chapala area had the exact same problem (refurb modems and faulty wiring).