HDFC Bank — non-working hdfc fastag

Dear support team,
In oct 2019 i have applied for hdfc fastag and got it in the last week of oct 2019. When i login to my fastag a/c, i found there was another vehicle also attached to my fastag a/c which does not belong to me. I called customer care no. And they assured me that it will be removed in 7-8 working days, but it didn't. From november, i started using my fastag, but found it to be not working at toll plaza. The staff there told me that it is not working. On 1st december, i made a complaint on hdfc customer care number and twitter handle. The customer care person told me that the same is being replaced at no extra cost. The twitter handle told me to dm all the details. From that day i have made so many complaints via tweets and emails, but they are not responding. I haven't even received any replaced card. I told them to cancel and refund my full amount, but they are not responding my messages.
Kindly help
Mandeep