I land in Auckland, naked, or at least feeling that way. I grab my 50-pound bag full of clothes and essentials and make my way to the Supershuttle, still lacking the two things that feel most essential. I don’t worry about it much, but feel the subconscious hum of anxiety escalate even after checking in at my hotel, even as I unpack a few things and begin to review my map. The first two stops I’ll need to make aren’t clearly listed on it.

There are two things I can’t feel comfortable without when traveling. The first is local currency. Holding just $50 or $100’s equivalent is more than enough to make me feel confident of being able to handle most scenarios. The more important missing element? A local SIM card.

T-Mobile has recently started offering unlimited international data to its postpaid, contract-bound customers, but data rates with AT&T remain robbery. Assessed at a per-kilobyte rate, each gigabyte of data while roaming overseas costs thousands of dollars without some sort of pre-selected roaming plan. I planned ahead, dropping $30 for a paltry 200MB, the same amount I spend for unlimited data and gigabytes of use per month at home.

For many, 200MB might be far more than enough for a couple weeks, but I tear through data service while traveling far more quickly than at home, where is still use it prodigiously. Between uploading pictures, tethering to my laptop, staying in touch via social networks, VoIP calls to friends and family back home, checking emails, using Google Maps to navigate, checking Yelp and TripAdvisor for reviews, etc, I could easily use 200MB in a few hours’ time. As such, this remains little more than an emergency oxygen supply; the more sustainable and affordable option is to find a local SIM card at most stops and pop it in for the duration of my stay.

I traipsed down Emily Place to Stockton and began walking downhill, partly from memory of maps I’d reviewed at home but mostly using common sense: down means water, water means shopping. Meanwhile, I looked around for a cell phone shop and an ATM. I made my way to Queen Street, still having found neither.

Using an ATM instead of a foreign exchange business means skipping most of the substantial fees levied by brokers. If you can stand it, waiting until you’re far from home and finding an ATM at your destination will almost always save you anywhere from 5-10% or more in money changing fees. At last, I spotted an ATM, but it was broken. Another appeared up the street. A few minutes later, I had colorful local cash in hand and just one objective left in mind.

Back up Queen Street, I discovered I’d walked right by just the store I needed. A cell provider named 2degrees offered prepaid SIM cards with a $5 one-time fee that could be loaded with 1GB of data for just $20. Perfect, I thought: 1GB should get me through three days. It turned out I blew through 2GB, since the place I was staying didn’t offer free Wi-Fi, which made it all the better value. The same 2GB would’ve cost $300 with AT&T, and that’s at the “discounted” rate offered for planning ahead. 2GB would’ve led to a swift bankruptcy at roaming rates.

If your phone is unlocked, I can’t recommend highly enough finding a local SIM card for trips longer than a couple days. Having access to all of your phone’s features can be extremely helpful, even if you’re not as tech-obsessed as I am. Being able to look up directions, hail a cab or Uber and make calls home for free using apps like Google Hangouts or Skype can be extremely valuable.