do they have an aircraft based at the heliport? do they have a dispatcher that needs to monitor t/o and l/d.
do they have pilot controlled lighting. Could be a close by hospital that has pilot controlled lighting on 123.025 and rather than turn on both while airborne they are assinged a different freq...
Its easy make a call on 123.02.... wait a few seconds.. nobody responds back switch to 123.05. ATC will give you a freq. change when you are clear of any traffic.