There may be a situation where you want to know who your wife is taking to. There may have been some change in her behavior and it may have made you suspicious that something is going on. If you are on the cell phone plan along with her then it can be easy to get a copy of the bill to see who the calls have been coming form.
The first thing you want to do is to get all the information that you can before you talk with your wife. If something fishy is going on she may try to hide it from you so make sure that you have all your ducks in a row so to speak before you speak with her.
Next if you call the cell phone company they will send you a copy of the bill. The bill will have all the incoming and outgoing calls so that you can see exactly who she has been talking with. It is best to know all the facts before you assume the worse.
if you have a chance to look at her cell phone you can also see what calls have been coming in and going out there as well. Make sure when you are doing this you do not get caught because it will make you look bad and if she is on the up and up then it can cause strain on the marriage.
If your wife has a totally different cell phone plan then you may not be able to get the bill from the cell phone company so you may need to check out what is on her phone but be cautious. Remember that people can get very angry when they feel violated.