They would already have done so in the Demand Notice U/s 13(2) clearly mentioning that they will proceed ahead with Section 4.
Also, they would also have published the notice in TWO local news papers.
It does not matter on how and where and to whom the notice was served. They have a clear guideline in place in the Act and they would have done that. It is not mandatory for them to serve notice to each of the defaulter in person by chasing each person door to door. They have provisions even to Affix the notice on the disputed property.