Airline Dispatcher reports repeated inability to contact enroute flights as required by FARs.

Narrative

I was given instructions to make contact with Flight 1234. I knew through the computer it was in the air; climbing to cruise altitude. I contacted Company Radio at approximately XA08Z; who was unable to contact the crew. After relaying this information; I was then given instructions to use a commercial radio operator to attempt contact. I did so. Shortly thereafter I received a Company Radio call from the crew of Flight 1234; which was passing over VUZ VOR at the time. Apparently; they had received the communication from the commercial radio operator; and decided to contact me through Company Radio; or Company Radio had finally made contact. After receiving a PIREP from the crew; I told them to disregard the communication from the commercial radio operator. The flight continued without incident. I believe this is the third report I've completed regarding the inability to contact an in-flight aircraft through Company Radio. This is a huge concern; since FAR 121.99 requires a fast and reliable means of communication with its enroute flights. As stated in previous statements; this occurrence (unfortunately) does not indicate that Company Radio is fast or reliable. I believe that ACARS system would be faster and more reliable.