Some polling agencies ask people to call a telephone number

Some polling agencies ask people to call a telephone number and give their response to a question.

List an advantage and a disadvantage of a survey conducted in this manner.

What sampling technique is used in such a survey?

Advantages

1) savings of time

2) cost of money is lesser

3) no labour is required

4) in a short time can be collected many data

Disadvantage

1) there is much non responses

2) they are collecting fata by phone not sure for accuracy of data

3) not able to collect measurable data