There are some limits and security measures set by the Reserve Bank Of India while doing transactions through UPI to ensure the safety and security of customer’s financial data. As you said you can’t make UPI transactions of more than ₹2,000 to merchants in a single day, which may be because of daily transaction limits imposed by your bank or UPI service provider.
I suggest you reach out the Kotak’s customer care and confirm the exact daily limit for merchant transactions with your RuPay Credit Card with UPI.