Invitation to pay from Italy

Hello! Today I need some advice from you. I am neither in Germany, nor where a traffic jam. On my first holiday in Italy, I did not quite understand the toll system. Long history! Today after more than four years, I received a letter from the Nivi Credit s.r.l. in this letter states that you have received the authority or special authorization of the Autostrade per L’Italia, to collect the outstanding tolls. Now I should pay about 46€. I have there At the motorway exit I had to pay already 25€ out of so-called reminder money. The whole thing is, as already mentioned over 4 years ago (14.03.2009). Isn’t that long a statute of limitations? I found nothing exact in the net. To similar cases, I leave it all for one year. Has anyone from you gained experience with such a payment request?