how to cancel registered POA

The husband needs to get a Deed of Revocation of Power of Attorney mentioning the date,reason and consequences of revocation of POA.

The revocation deed is registered by the same authority that registered the POA.

Then the Deed of Revocation of Power of Attorney is published in a local or national newspaper.

A copy of the Deed of Revocation is to be sent to the wife also.

The revocation of registered power of attorney deed is to be executed jointly along the power agent before the concerned sub registrar hence it is pertinent that the power agent is informed about the decision to revoke the same in advance by a notice and a public notice is published in a local newspaper to this effect. 

Get a cancellation of PoA registered, published in local newspaper(s) and sent a copy to your wife with a legal notice to stop further dealing on your behalf.