Well I know for airpush you either donate to the airpush developers on their site, uninstall the offending app, or give them your imei( supposedly so they can include it in their exclusion db or something ).
Xapush may be similar, or if you know what you're doing you could decompile the apk, remove the ads, and then recompile it but don't distribute it unless it was a free app( and give credit to original dev ).
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