I need to stop a charge from Apple that is pending

Standard procedure is to pay for the item and then ask for a refund. I suspect if Apple offers the ability to cancel a pending purchase they would have included it in their online store features.

Request a refund for apps or content that you bought from Apple - Apple Support

Please call or iMessage Apple Support directly; ☎️ 800–692–7753

Did you click the last line in Limnos' post? It is an Apple Support article that explains the refund process.