What should I do if my old iPhone is still connected to iCloud?

i sold my old one without logging out my icloud and whatsapp account so im just reset my old iphone..when im syncing my icloud into my new one ..i see it still connect with my old phone.. i cant remove it because it say to wait until next week for new device.. so when im downloading whatsapp..verif code said to check on my old iphone..and then when i request with sms code it say not safe application.. i think because it still connect so whatsapp think that as a clonning application..can anyone help me? i need my whatsapp because it contain my work there 😭😭

[Re-Titled By Moderator]