All solvents can have an effect on the chemical shifts of the solutes, even the TMS. That is why the solvent is noted in determining the NMR. If you obtain a spectrum of the same sample in a different solvent, it is not unusual to see small to unexpected shifts occurring.
Without the structure being given, it is very difficult to predict the purpose of using benzene. When I was in grad school (years ago), I used benzene to induce shifts in methyl ketones to determine whether they were axial or equatorial by the difference in the shift in benzene.