Unfortunately there are only two confirmed phone calls made and even the timings of those are questionable to some extent, they were 26 years ago and they aren't going to get any clearer due to the passage of time.
The call from JB to JM, which JB changes when that call was made in his statements, and there are witnesses at JM's end which indicate further discrepancies, although how reliable they are is for you to decide.
And the other confirmed call is from JB to the police, again there are discrepancies surrounding the time due to the two police phone logs giving the time of 3:26 and 3:36, however with this call we are a lot more confident about the time being 3:26 due to the time of JB's arrival at the scene.