Well, this kind of scifi is bending the laws of physics. Thus, you can fully legit use hypothetical particles which aren't proofed to exist yet.
So your solution is as simple as it can be:
A tachyon /ˈtæki.ɒn/ or tachyonic particle is a hypothetical particle that always moves faster than light. [sic]
[...]
They have been used as a standby mechanism upon which many science fiction authors rely to establish faster-than-light communication [sic]
A common mechanic is sending a tachyon beam to the communication target. Behaves pretty much like any light beam (Just faster), can be detected or blocked by objects on their way.
But even Tachyons would have a big problem. When the tachyon wants to reach a spacecraft from behind, it has to pass streched space, which will make it relatively slow, maybe so slow, that it needs aeons to reach the spacecraft.
There are two solutions for this:
- Warp-drive is slower than tachyons by the manner that the time a tachyon beam needs to pass the negative warp-space is reasonable.
- Spacecraft has to stop or throttle warp-drive to get the tachyon-delay reasonable.
First solution has the disadvantage, that the spacecraft has to move slower than it might could. Second solution has the disadvantage, that you can't tell the crew "hey guys, I wanna talk to you, throttle down please." due you can't communicate currently. Thus, the spacecraft would have to throttle down periodic and the in-warp communication would have a protocoll like: Once in t(xy) the spacecraft throttles to speed v(tachyon)-xyz), then communication is done, then the spacecraft accelerates again.