As per the platform announcement/tweet and email in September and follow up in October 2014 regarding the paid privacy service – please make sure that you have set pricing for the service if you DO NOT want it to auto-renew on a domain that has it enabled.
If you do not set the pricing – when a domain is renewed with the service enabled, the PP service will automatically renew with the domain and you will be charged. Thus to avoid this – set customer and reseller pricing in NEO >> Settings >> Manage products and pricing >> Domain Registration >> Privacy Service (on the right hand side of the screen).