From a classic SIM to Micro SIM - and it worked!

After using a 'classic' SIM card for many years I reached a point where I had to switch to a phone which no longer supports big SIM cards. Here´s how it went...

With my old Samsung Galaxy S3 mini getting slower and the battery discharging quite quick the signs are clearly showing for a change to another phone. Which I got. From a bank. And even for free. It´s a LG K5 with two SIM slots. But more about that another time.

I was aware that it was possible to cut your SIM card to a smaller Micro SIM with a cutting template, but I never tried it before. Now, while being in Germany - in proximity to my service provider if anything goes wrong - I gave it a shot. 

I printed the template, cut the lines as suggested easily with a scissor. After the important cuts were done I switched to a nail file in order to make the card fit properly and getting the lines more accurately. Initially it did not work. Tried the file again and the card was in. I booted the LG phone and the PIN was requested! Great, it worked.

But for some reason mobile data did not really work, even after a few minutes. I mean the 'E' (edge) letter was seen at the top, so 'Data' was basically on. First I expected that may a part of the SIM got damaged. Or even the slot? I tried the second slot, issue the same. 
Refiled the SIM again a bit and put it back into the first one. Issue remained. But there was some data transferred, just a few MB, but opening Google and other sites ended in a timeout.

So what about the APN settings? They looked kinda old, so I checked for other settings for German T-Mobile:

Name: T-Mobile

APN: internet.t-mobile

User name: t-mobile

Password: tm

Changed the settings, rebooted. Waited a few minutes for changes to apply and then it worked. In hindsight, maybe the old settings would also have worked if I had waited a bit longer, but anyway:

The SIM card cut worked!