Assalaamu alaykum. When I complained about the reduced speed of my internet connection to my internet service provider, I told him that I was getting maximum 138 kB/s speed of internet, which was 2-3 kB/s less than the actual maximum speed that I was getting (actual speed might be 140-141kB/s). I told a lie to him so that he would increase my net speed. This lie was unnecessary, as my internet's maximum speed (192 kB/s) is limited by the package which I have to pay for every month. That means that I have the right to get at least 192 kB/s. The fault was in the internet service. So the purpose of lying may be to make the internet service provider more concerned about my complaint, which also seems unnecessary. After the complaint, he resolved the issue immediately. Now I am asking myself whether this lie made my internet connetion impermissible in any way. If it is impermissible, then what should I do?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

It is not permissible for you to lie to the internet service provider, even if you are entitled to the service. In principle, it is forbidden to lie except for a valid excuse. The Prophet said, "Beware of lying, for lying leads to wickedness, and wickedness leads to Hellfire." [Al-Bukhaari and Muslim]

What you mentioned does not allow you to do what you did, but if it does not result in you getting what you do not deserve, then there is no harm on you to benefit from the service. Seek the forgiveness of Allah for lying, and be determined never to repeat it.

Allah knows best.