At first she didn't want to use such services, since she thought these were not legal. I had to inform her that you have the full right to know who is calling you. Especially in this case, when the cell phone calls were really annoying and became something harassing. Second thing which my aunt didn't like was the small fee, which is usually charged for reversing a cellphone number. I had to explain her that these few bucks are a pretty fair price for a peace of mind.
This was my aunt history, but you certainly may have different reasons to look for cell phone tracking by number. To sum up the few words I wrote above: such cell phone lookups are completely legal and you don't have to worry you will get into trouble by using it. Second very important thing is that there is no chance that the holder of cellphone you're tracking will figure out that you're checking his cell phone. Cellphone tracking services offer you 100% privacy guarantee which means it is impossible to reveal your personal details to cellphone number owner. Regarding the small fee, you shouldn't complain about it, although there are a lot of "free" services, you will get any good results with them. And believe me, the results from fee based phone tracking are well worth the tiny price they cost.
If you're still worried about money, remember to always check the service provider's policy on moneybacks. Just make sure, that in the case you are not satisfied with the results of the search they will refund you your money. Playing with charge backs can be really pain in the neck, so as always, before paying for anything, check to terms and conditions of your chosen service plan.