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Question about switching SIM cards when traveling

Hi everyone! I am a Verizon prepaid customer, so I don't qualify for their astronomically expensive international travel plans. So I figure the cheapest way to acquire cell phone service in London next month, is to buy a local SIM card when I get there. My phone is unlocked and quad band (Galaxy S7).

Have any of y'all ever had trouble when switching SIM cards? I've never done it before. Does your phone require that you enter a PUK (unlocking code) when switching back and forth? Is it a hassle? Do you prefer keeping a second travel phone? Thanks!

Posted by
8889 posts

Switching SIM's is a one minute job: Turn off phone, remove battery, remove SIM (usually hiding under battery), put in new SIM, put back battery and cover, turn on phone. You can practice before you leave home.
SIM cards can have a 4-digit PIN which you enter whenever you turn on the phone, for example if the battery went flat. This is a security feature to stop stolen phones or cards being used on your account, but many people disable this.
Note the PIN belongs to the SIM, so when you put back your originla SIM, you re-enter its PIN.

The PUK is a longer backup code which you only need if you have put in the wrong PIN 3 times, which like most passwords blocks the PIN.
When you get a SIM, the envelope it comes in should say the PIN, PUK and the telephone number.
Try not to loose your original SIM, it is very small!

Sounds like your service provider is a rip-off merchant. European providers automatically provide roaming (use of phone in a foreign country) at about +25% or +50% of normal charges, and they are trying to reduce that surcharge.

Posted by
262 posts

I am a frequent traveller and only use prepaid for this reason. I have a current iPhone and it takes two seconds to switch the sim cards, enter the unlock pin code and use the phone. I don't have one for London, so others would be better able to answer questions about a specific plan for the UK.

Posted by
2525 posts

"Sounds like your service provider is a rip-off merchant." Well, we do complain here about the rates, which are slowly changing due to the build out of the system and some level of competition, especially in urban environments. Balancing that a bit...America is a big country and my state is larger than Germany with 1/8th the population of Switzerland (more cows than people). That makes for much hardware given the customer base. On a bright note, Verizon now offers use of one's existing plan in Canada and Mexico for a $2.00USD/day charge.

Posted by
40 posts

Thanks, everyone! Yes, Verizon is indeed a rip-off merchant, but they provide the best coverage in my area. And their prepaid plans are reasonable. I'm very excited about my first trip to London - thanks again! :)

Posted by
167 posts

I do not use my USCelluar smart phone to make calls when I am in Europe. I do use the Wifi constantly, however, never have any problem finding wifi and it costs me nothing.
But to answer your question directly, I have a cheap, unlocked cell phone that I bought in Italy 3 years ago, and have swapped out SIM cards in Spain and Portugal, and then put the SIM for Italy back when I return there.

Very easy to do, and SIM cards are available in most airports. My original investment of 20 euros for the phone that I have used for 3 years is a cost savings for me.

Posted by
823 posts


If you must remove your Verizon SIM from your phone (I'm not familiar enough with the Galaxy 7 to know), I would bring a small plastic case, such as a SD memory card case, to put your Verizon SIM in to safeguard it. They are very small cards and can easily get lost. Also, if you purchase your London SIM from a phone store (I used O2), you can watch them install it so you know how to re-install your Verizon SIM (if required) on return.

Another bit of advise, I would re-install your Verizon SIM at the airport in London just before boarding the plane. The departure lounge is bound to have much better light and you'll have much more room to maneuver in case you drop one of the SIMs. Being on a dark and crowded airplane while changing the SIM is inviting Mr. Murphy to participate...

Of course, this may all be moot considering the problems with Galaxy S7 and Note 7 battery problems - it may not be allowed on the plane...

Posted by
823 posts


Upon googling "Galaxy S7 SIM Installation", it looks like your SIM slot is part of the micro SD card tray on the top edge of the phone. Be sure to take the drawer "key" that came with the phone or a small paperclip in order to extract the tray.