The best chat if your getting attacked would be English or World chat. Spam is considered the overuse of the same words like if you say HELP ME like 10x that's spam. If you don't have a guild and your a lone wolf I'd definitely suggest finding friends that can also help you during this time. If your getting attacked you can also use the yell option in the local chat, but odds are someone might not be around. Advertising would be a second option sure because it says if you need help with someone then others will help you. Once I had a situation where I was on my noob character on a PVP server and I asked English chat for help (at the time I think it was Game-Chat) and no one seemed to care, however I did type in advertising and someone did seem to care but it didn't matter in the end it was too late because I was a noob. Making friends on PVP is your best bet! I'd recommend joining a guild. Ultimately depends on your world how popular it is, how helpful the players online are at the time, and if you have a guild or not.