Bottas penned a one-year deal at Mercedes this year, making the switch from Williams, and he has impressed on his debut for the Silver Arrows, clinching victories in Russia and Austria.
The 27-year-old is currently third in the Drivers' Championship, 19 points behind team-mate Lewis Hamilton in second and 33 points adrift of Ferrari leader Sebastian Vettel.
Despite the strong start to life at the Brackley-based outfit, the Finn is yet to open negotiations about extending his stay and he admits the situation needs to change sooner rather than later.
"For sure, soon we will start to… we need to speak [about] what's going to happen, obviously," he said. "I have no idea about the future yet so, for sure, we will speak at some point, but the problem is that the mobile phone is not so good in the sauna!
"It doesn't work, so it could take a while, so don't expect anything in Spa..."
The Formula One season is currently on a summer break but action will return at Spa-Francorchamps on August 25-27, where Vettel will be looking to carry on from his victory in Hungary last time out.