It is one direct train only. Both for passengers boarding at Amritsar and boarding at Chandigarh.
@ 2926 is called the main route of - Paschim Express (Amritsar to Mumbai Bandra Terminus).
2926A is called the slip route of the main route of Paschim Express. (Slip route means few bogies of a train from Kalka are detached at Ambala Cantt and attached to the 2925/Paschim Express. The route from Kalka to Ambala Cantt is called and known as slip route of Paschim Express.
@...
more... Chandigarh falls on the slip route of Paschim Express.
@ Note that there is not shifting by passengers at Ambala station but bogies are detached from one train and attached to another train. That's all.