contactsiphone
A large proportion of contacts I have gained over the years have more than two current numbers.
Examples include: home, work, mobile; home, NZ work no., US work no., Spanish work no; etc
I have only worked out how to add two numbers to particular contact; after that, when you click add there is no other options.
This is crazy, this is 2010, I must be doing something wrong, can you help me out?
A custom label will have to suffice here. I have many contacts with their cell phones listed as 'mobile', and then a custom 'Google Voice' labeled number.
[edit]
An alternative to this is to make the change via Address Book.app on your computer, then sync the contacts to your phone.
Custom labels are available in all contact adding/modification screens.
First, browse to a contact, and tap the label name (to the left of a phone number, e-mail address, etc.). You will see the list of labels.
Second, swipe all the way to the bottom, and tap on "Add Custom Label".
Type in a new Custom Label;
And then it will be displayed next to the number.
It will now appear in a list of custom labels on later access.
From your question, I think your setup involves syncing contacts with Google, a computer (Mac?), and an iPhone. Syncing with Google has been a pile of poo since Mountain Lion. For me, it kept duplicating contacts, bringing back deleted ones, and as you mentioned, swapping the contact information between contacts.
Since neither Apple nor Google seem to care about fixing it, my solution is to use iCloud to sync contacts between the Mac and iPhone. (This seems to be Apple's preferred method, so it's the one in which bugs will likely be fixed the fastest.) I periodically upload a vCard of my contacts to Google. This is a lot less work than hunting down all the contacts that syncing with Google messes up.
Best Answer
I can add as many phone numbers as I want on the iPhone. When you're in edit mode in the contact, there's always a blank line under current phone numbers where you can start typing a new one.
If you click on the label of the number, you can select a label (work, home) and even a custom label if you scroll to the bottom of the label selection list.