Pros
The top strength of Telmex is its people, "Telefonistas" is a brotherhood and a way of living, proud of belonging to the company. Also you get over the law benefits, and becoming part of the largest corporate groups you have "employee" benefits in all possible verticals, banking, hospitals, tires, dinning, hotels, etc. You will be constantly trained because Telmex has it's own Teaching institute "Instituto Tecnológico Telmex" with constant training. Also you will be working with the top partners since everybody want to work with the leader of each industry and that is the case for TELMEX.
Cons
The archaic management is a huge pain, all the time you are expected to accomplish "on your working station" hours rather than objectives, if you stay on your spot, and one untold history is that you have entry time but no leaving time, so it's common to be working 7 PM or later. Also some managers use the lead by fear strategy or always excusing all the excessive demands under the name of the CEO "Slim" but it's just the way to force their team to achieve without asking.