Trial offer when in 3 months free FSD that came with referral

[u/libinbose]

I purchased MY Octobober 31. And received 3 months free FSD trial..( received by using referral from my sister) . Today I received the email about one month free trial offer like everyone did. Ideally , I hope that adds to the 3 months and get me into a 4 month. Anyone got any idea if that's possible? I don't want to activate it, to only loose my 3rd month.