Name of Internet Service Provider (ISP)
Orange

Country of residence
France

Reference number from your ISP, if you have raised this matter with them
They didn't give me reference number, they said they "were not concerned".

When does the problem occur (e.g. only during specific times such as in the evenings?)
It seems alright during the day, but it gets progressively worse. The peak of latency starts in the afternoon, and the game becomes unplayable in the evening. Since I can't change my working hours... Well. I can't play Final Fantasy XIV at all =/

Frequency of problem (e.g. every 2 minutes)
Whatever I'm doing, every 5 seconds or so.

Game content in which the issues occur (e.g. dungeons, trials, certain areas)
Dungeons, trial, gathering, typing, breathing, walking, riding a chocobo. Well. Everything.

IP address (optional)
And it'll stay optional =D