FROM the moment you first cradle your newborn son or daughter in your arms, you have got just one job to do.

The feeding, clothing and nurturing is minor and incidental to the main task.

Getting up to them in the night, drying their tears, cheering them on in the football team, helping with homework, this is all just everyday, run-of-the-mill stuff.

Even as we read them bedtime stories, kiss their grazed knees and blow up their armbands, we know that all of this is a precursor to the most difficult job of all – to get rid of them. Not from our lives, of course, but out of the house, to set up on their own and become fully independent, self-sufficient human beings, capable of looking after themselves.

I didn’t think it would take us until they were in their mid-twenties.

In these days of student loans, crippling rents and soaring living costs, parents, unlike those of previous generations, can’t simply cut the purse strings once their offspring turn 18. When our older boys left university and got jobs in London, they needed help to pay their first month’s rent plus the sizeable deposits required to secure their accommodation. And on top of the exorbitant cost of living in the capital, the money they had to shell out on getting to and from work alone was a struggle on a starter salary.

But they did, slowly and surely, become independent, apart from one last lingering financial tie to us – their mobile phones. For us, this is the last, and most difficult, cord to cut. For the boys, it has been particularly traumatic.

We got them all their first mobile phones when they were 11. Even though they rarely answered our calls or responded to texts asking them where they were and what they were up to, we felt it was an important lifeline. And so we continued paying, long after they started taking responsibility for themselves in other areas of their lives.

While the concept of cutting the apron strings has never bothered them, the mention of cutting mobile phone contracts induced howls of protest. For a start, they will all have to learn how to stay within their data limits and pay the hefty charges accrued for going over the contract allowance (easy to do when you’re not paying the bill). It happens at alarmingly regular intervals in our house, which causes my husband, the account holder, to see red in more ways than one, and threaten to cut them all off.

For son number one, we decided the time had come as he approached 25. As it was, we had to give him a year’s notice to get used to the idea. He needed time to prepare.

In the boys’ defence, they’re not helped by the ridiculously complex packages offered by mobile phone companies, which tie you into unnecessarily confusing financial contracts hardly anyone understands. Few of us have a firm grasp of how much we talk or how variable that is. And now that we call and text less, we are paying for hundreds of minutes of free calls and unlimited texts we rarely use.

But since we have all started using data more, we have even less of an idea of how many gigabytes watching a short video someone has sent us on WhatsApp, or reading an article online while we’re in a long supermarket queue, is likely to equate to.

We would never agree to pay for our petrol, or groceries or electricity like this, tied down to stumping up so much every month in a two-year contract, then paying punitive charges if we unexpectedly use more, while gaining nothing if we use much less.

Mobile phone companies could, of course, come up with more straightforward pricing packages, related to actual usage each month, but this would be far too easy, and much less profitable.

In the meantime, it’s a financial minefield, which son number two, who is an academic year behind his older brother, and therefore has had an extra 12 months to prepare himself, is about to enter in December.

For son number three, the time is fast approaching.

It’s the final cut and it’s not going to be easy.

Life was so much simpler when all we needed was a bag of coins to call our parents occasionally from a phone box.