Hi @Sriram Sambasubramanian 

Just because the SIM card has been activated does not mean that it will work immediately, after that the number must be ported from your old provider.
Have you already received a message (email or text message) that your number has been ported to KPN?
As long as the number has not been ported, you must continue to use the SIM card from your old provider.

You must also take into account the end date of your contract with your previous provider and a one-month notice period, after which the number can be ported.

What date is stated in the emails or documentation you have received?

My previous provider is a Lyca Prepaid SIM... 

I don't have a specific end contract date... I did not receive any message from KPN that Number has been ported .But received an SMS from KPN asking to send YES to 6688 for porting…

Should I send this message from the old Lyca SIM?I am not sure if it is possible as I have used up my balance & I don't think I can recharge now ..

As it is a prepaid SIM,I can't do much either... I can't make any calls or send SMS.. Requesting help on probability.. 

You have to, @Sriram Sambasubramanian.

If you don't send the YES, we won't port the number. And the YES has to come from the number you want to port. So, you will have to use the old sim.

As long as the number hasn't been ported yet, the old prepaid should work as normal (if it has balance). Which means you should be able to add balance to it. 

@Erik van KPN @GeSp 

Many thanks for the Swift Response... Number Portability is complete & I am able use my new activated KPN SIM…

Thanks and Regards

Sriram Sambasubramanian