If Catholics have to be open to new life how can they practice Natural Family Planning? I listened to a Christoper West audio recordings where he explains the theology of the body of JP2 writings.

He keeps on saying how important it is to be open to new life within the marital act(sex). Using contraception is prohibited because it violates the very act of love.

I noticed though among Catholics who practice NFP (natural family planning) that they solely use it to prevent new life. I'm talking about people who have no problem to conceive a child. I never hear them saying we are trying to conceive a baby. I only see the announcements how they 'again' got pregnant unexpectedly. Probably because they made a mistake in calculations or couldn't abstain. 

My question is: Doesn't this set NFP to the same level as contraception? Does the child always need to be expected?

I know there is nothing wrong to have an unexpected baby or to postpone having a baby. Don't the couples' always trying to avoid pregnancy changing the meaning of NFP use? Didn't it become to be 'open to new life but always try to prevent it'?
This sounds like a great question to ask on Catholic Culture but since that's not up, I'll give it a shot here.

If therefore there are well-grounded reasons for spacing births, arising from the physical or psychological condition of husband or wife, or from external circumstances, the Church teaches that married people may then take advantage of the natural cycles immanent in the reproductive system and engage in marital intercourse only during those times that are infertile, thus controlling birth in a way which does not in the least offend the moral principles which We have just explained.
Neither the Church nor her doctrine is inconsistent when she considers it lawful for married people to take advantage of the infertile period but condemns as always unlawful the use of means which directly prevent conception, even when the reasons given for the later practice may appear to be upright and serious. In reality, these two cases are completely different. In the former the married couple rightly use a faculty provided them by nature. In the later they obstruct the natural development of the generative process. It cannot be denied that in each case the married couple, for acceptable reasons, are both perfectly clear in their intention to avoid children and wish to make sure that none will result. But it is equally true that it is exclusively in the former case that husband and wife are ready to abstain from intercourse during the fertile period as often as for reasonable motives the birth of another child is not desirable. And when the infertile period recurs, they use their married intimacy to express their mutual love and safeguard their fidelity toward one another. In doing this they certainly give proof of a true and authentic love.
Bl. Pope Paul VI Humane Vitae p16

So, you've got good cause to be concerned.  However, I don't think one ought to level a blanket judgement on any couples motives for using NFP until one gets to know them!  And in getting to know them one can suggest a deep-dive reading into the purpose of the marital act as unitive and procreative.  If at that point you want to &quot;council the ignorant&quot; then, by all means go for it, you'll probably get a better reaction than if they used other forms of contraception!
Dr. Janet Smith says in Contraception Why Not that it is the conversation that couples have each time they make love which makes NFP different.  The conversation around love making and the openness to children each time makes a world of difference. The conversation can include reasons you don't want to have kids right now, reasons you do want them, differences of opinion.  But there's no inherent barrier to baby making, I think that's openness and living in accord with God's plan for your family.
Then, each act is not a question of whether or not to use a condom, but whether or not it prudent to have a baby. And prudence, oddly enough, is the chief of the Cardinal Virtues.