Telecom operators are selling discounted add-on lines with their packages to reach potential customers who cannot afford a mobile phone line or who are too young to sign up for one.

The novel feature: Rolling over unused SMSes and calls to a second user.

Most cellphone lines come with contracts that give hundreds of minutes of free talk time and a set number of free SMSes, but not everyone uses his entire quota of these freebies.

Lecturer M.K. Wong, 52, for example, struggles to use up the talk time on his $30 subscription plan - even as his two teenage children jointly chalk up $200 in monthly phone bills.

Of the idea, he said: 'If we can share everything, there's no wastage.'

StarHub and SingTel have started offering add-on lines for a fixed monthly fee of about $10 a month.

StarHub launched its deal a week ago and threw in 1,000 free SMSes a month as well.

SingTel's RedPac service gives up to $160.50 worth of free calls between parent and child each month.

SingTel spokesman Chia Boon Chong said the response to its month-old service has been 'very positive', but declined to give figures.

The offers from SingTel and StarHub are aimed at grabbing new customers and keeping existing ones, industry analysts say.

Competition will get even fiercer when number portability - to start in June - gives users the freedom to switch telcos without needing to change their phone numbers.

Mr Marc Einstein, a senior industry analyst at research firm Frost & Sullivan, predicts that telcos will be even 'more generous' in their deals in the new competitive climate. A family deal at one price, with talk time that can be shared, is not a long shot, he added.

For now, the shared deals work out better for parents who want to tag on their children whose bills are small.

Photographer Julian Tay, 45, said he signed up for SingTel's RedPac a fortnight ago to share his bill with his 13-year-old daughter.

She had used $20 stored-value cards.

Said Mr Tay: 'My line wasn't used much anyway, so why not share it?'

The only cellphone operator that has yet to launch such add-on deals is M1.

It offers a service that lets a second user piggyback on a main line, but does not allow sharing of unused talk time.

siewtha@sph.com.sg