There are dozens of options.
First, if you have a phone line, you ALREADY have IMMEDIATE internet access. These are direct "no sign-up required" so-called "free" access services, which basically means you`ll be paying for the phone call at regular voice-call rates. For only daily e-mail use this is the best and cheapest.
Off hand I recall the easy to remember "Alternativa Gratis". numbers are 5555-5555, and 5353-5353. User and passwords in this and most other "free" services are usually GRATIS, but in this case ALTERNATIVA also works as the user. I never checked but I wouldn`t be surprised if ANY pw worked.
This option is great while you wait for high-band installation, or when said access is temporarily unworkable.
Then you can sign-up for cheaper half-rate phone access, but these only save you money if you use them between an hour to 4 or 5 hours a week, average (about 20-25-pesos/month). For less time the "alternativa gratis" system is best, no bills, no up-front payments.
For more than 5-6 hours a week, high-band begins to make more sense, and is more economical. I have seen some as low as $25-$30, but be aware of the limitations.
You need to check all plans and compare rates, versus speeds and access times, and factor in your usage profile. Some plans, mainly phone company ASDL`s seem cheaper, but have limited access time in minutes per month, or data rate transfers, after which you will be charged for additional minutes or data blocks.
I have fibertel which has flat-rate, unlimited usage but it seems to be much slower than the advertised, 1Mega-rate. I would need to take the time to confirm since apparently local websites are accessed much quicker than sites in other countries.
Either way I save a chunk off the price since I also have Cablevision, without which the cost would be outrageously high. $90 vs $130.