Large Transport; Low Wing; 2 Turbojet Eng
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 13
Communication Breakdown
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Taxiway
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented
Human Factors; Procedure
Aircraft X was given taxi instructions after crossing Runway 25R; to taxi via Bravo; Bravo 5 and Charlie to the ramp. Aircraft Y was also inbound to the ramp but missed their turn.  The CPC-IT gave instructions to Aircraft Y to taxi via C4; B; and C6 to the ramp.  The CPC-IT then told Aircraft X to give way to Aircraft Y at C6 and contact the ramp (Aircraft X had made a few attempts on our ground frequency to contact the ramp.) Aircraft X acknowledged their instructions and advised us they had been attempting to contact ramp control but nobody answered them and they did not want to enter the ramp without authorization.  Right after that transmission; somebody keyed up on the frequency and stated; 'Aircraft X; you have been calling on ground'.The timing of that transmission as well as the demeanor of the transmission lead me to believe that the ramp controller keyed up on the ground frequency (121.1) and made that transmission. I was performing OJTI at the time. I reported the incident to my FLM (Front Line Manager) and OM (Operations Manager). My recommendation is to not let a ramp controller have the ability to key up an FAA frequency. I would also change the current LOA between the two facilities to have the ground controller issue a ramp entry point and no longer have airlines contact ramp control on the movement area.
LAS Ground Controller reported a communication breakdown between a Ramp Controller and flight crew.