What are the rules against hard-sell tactics at MRT stations?

Of late, there appears to be more and more young people at many busy MRT stations, both inside and outside, canvassing for donations, marketing products or conducting surveys.

It is perfectly acceptable as it is a source of income for them and an opportunity for some of us to help those who are needy.

What, in my opinion, is not acceptable are the hard-sell tactics and persistence of some of these people.

They are not prepared to accept a polite "no" or a "no time" as an answer, and will trail and pester people until they capitulate.

This is annoying and a nuisance to passers-by.

Does the Land Transport Authority and the relevant authorities have any rules and regulations governing such activities?

Ronnie Poon Beng Choon