Businesses have been trying out new marketing initiatives in a bid to get around the Do-Not-Call Registry, which came into force on Thursday to prevent unwanted calls and text messages.
Some have contacted consumers to seek their consent to offer them marketing materials.
Others tried their luck by spamming consumers with advertising text messages before the registry kicked in, marketing players told The Straits Times.
By listing their numbers on the registry, consumers can block telemarketing calls and texts.
Companies must now check the numbers they call against the registry every 60 days.
This will be cut to 30 days from July.
Telemarketers who call numbers listed on the registry risk a maximum fine of $10,000.
Several multinational corporations have sought explicit consent from customers to send them marketing materials.
Cerebos Pacific, the maker of Brand's Essence of Chicken, did this last month.
A spokesman said the company is "committed to upholding and respecting our customers' rights to privacy and personal data protection".
Another firm that is understood to have sought explicit consent from customers is beauty product maker Clinique.
Ms Lisa Watson, chairman of the Direct Marketing Association of Singapore, said getting clear and unambiguous consent from consumers is the "gold standard" for marketers, adding that larger companies should have the means to do so.
But Ms Angie Tay, vice-chairman of the Contact Centre Association of Singapore, which represents call centres in the Republic, said small and medium-sized enterprises may not have the resources to comply with the registry.
As a result, some may have carried out a mass marketing campaign last month.
"That might be the reason why many people received more text messages last month compared with other months," Ms Tay said.
She believes companies may now look to alternative methods, such as e-mail and social media, to reach customers.
Ms Watson noted that few companies would have mass-spammed consumers as they would not want to damage their relationship with customers, and pointed out that a rise in the number of marketing messages may also have been due to the Christmas season and year-end bonus period.
She added that some consumers could have even thought they received more messages last month because they had added their numbers to the registry.