Mythbuster: Could chipped Callcards be recharged by leaving in the freezer or covering chip with Tipp-ex

If you collected Callcards or even just used them back in the 1990's you have probably come across a number of claims how to recharge or replenish units on a used Callcard. Some of these methods include:

1. Leaving the Callcard overnight in a freezer
2. Covering the chip in Tipp-Ex/correction fluid
3. Covering the chip in nail varnish

So the question is was there any truth to any of these "tricks". Did they work? To answer these questions we first need to understand how chip cards actually work.