I think you just have to look at other countries that are doing this. In Italy, for example, they have PosteMobile. They do sell Internet. They are bringing in profits. In 2015 it was 31 million euros, which is up from 14 million euros in 2014.
The French also have a system, La Poste Mobile. It now holds 1.3 million telephone lines. They had an increase of 10% over 2015, as of June of this year. La Poste Mobile revenue increased 6.4% at the end of June 2016.