I had this issue. It would only allow me to use the phonebook and voice recognition up to the letter "P". I'm not sure if that's 1000, but I don't think there was a way to get it to work in the idrive. You can use your phone to dial and it would still sync to the idrive for others that were passed the cutoff.

Alternatively, I deleted some names and now I can call Zephyr Zegan without an issue through voice command.