Istanbul to Belgrade by Train

Hi
I'm planning to travel with Train from Istanbul to Belgrade. Train will pass through Sofia. I have a visa for Serbia/Belgrade but i don't have visa for Bulgaria(Sofia). And After Serbia i will continue to Montenegro (i have visa). Anyonw here can guide Do I need to get Visa for Bulgaria? Or its not required If I donot get off in Sofia.
Any suggestions please...

U need visa for bulgaria, yet if you have schengen you don't need

I see :(
Thanks :)

You are welcome :top: