Vodafone Idea - All the features of International roaming not activated

I have a Vodafone number. I have been using this number for the last ** years. I had activated international roaming on **th April **** for * days. I was travelling to Singapore.
Vodafone activated my international roaming with the plan of Rs ****/-. on my request which had free voice call -Incoming and outgoing calls, SMS and also free data.
But I reached Singapore, I could only connect to voice service. I connected to the right carrier as suggested by the customer care executives. I was unable to connect to data.
I tried contacting the customer care executive on * to * times. All the solutions provided by them failed. All setting suggested by them did not work. I activated the pack of Rs. ****/- for all services including data. I could use only voice services and could not utilize data service due to poor service by Vodafone.
I demand cancellation of appropriate amount from my billing. I think I should not be liable to pay the entire Rs. ****/- as I could not use data service due to Vodafone bad service and non-support in resolving the issue. My issue was Vodafone denied data service during international roaming which was the part of the pack.
Moreover, when I contacted your customer care, they could not help me with the problem.
I email and subsequent telephonic with Vodafone executives, but their approach was towards solving my data pack issue was poor and never look to help me. Rather it was to protect their own interest. This is daylight robbery and cheating. Vodafone is charging the customer for service, which fails to deliver.
I would request Vodafone to reduce my bill amount with the appropriate amount for not providing data services during International roaming.