Plat Sup Spamming Janna. LF duo

I don't know how many times it's been already that I hit plat 4 promos and win, only to drop back as soon as I get in. Please. I mostly play solo q, but I desperately need a good duo to play with me to secure victories because there's only so much I can do. If you are smurfing, I promise I won't be heavy. The highest I've been is plat 2.