This post is not related to batteries, or toothbrushes, but rather to mobile phones.
When switching your pay-as-you-go mobile phone from one network to another, there is often a small amount of leftover credit remaining on your old PAYG account. If this is not used up on calls or texts it will be lost forever into the coffers of your old provider. As an alternative, you can donate the remaining balance to charity through JustGiving – and specifically to Oxfam UK through the text donation page set up for this purpose. The page gives full instructions for how to use your leftover PAYG balance for a donation to Oxfam.