I've seen hundreds of signals services and other signals providers claim accuracy close to 100% or even 100%. Those fall into these categories:
1. Someone got VERY lucky for a short period of time and really believes he/she has uncovered The One and only Secret to incredibly profitable trading. The moment the market shifts from whatever short term pattern they detected, they crash and burn. Don't worry, they'll keep trying and will make a handful of good trades on a trend and will be back with their new and improved secret method.
2. Gross exaggeration. Someone might be doing adequately, but doing adequately isn't what's needed to attract clients. A tiny number of these may be adequate for the long term, but they are very hard to tell from:
3. Lying scammers. There are numerous ways to fake a trading statement. These people might have a system or they might be guessing wildly. Either way, they don't care whether you win or lose. All they really want is to collect money. If they build up a bad reputation, a new website is all they need to roll out a fresh set of fake claims.
You are effectively asking for a money printing machine. If it was that easy, why don't people like Warren Buffett and George Soros invest a couple million dollars to find 10 perfect or near perfect signals providers and offer them an exclusive contract to trade multi-billion dollar accounts? If these signal providers could do what they claim, spending a couple of million to find the hidden successful ones among all the scammers and overconfident new traders would be a tiny investment that would result in far better results than anything Buffett or Soros ever achieved.