This is a colloquial particle combination that serves two main purposes. One, it functions like 'speaking of' but with a complaining tone, often when you want to change the subject or point out something obvious. Two, it attaches to a name or word you've already said, meaning 'I told you already' or 'you know', with a hint of exasperation. It is very much spoken Japanese, often used in arguments or when you're fed up with someone not listening. The nuance is 'come on' or 'for crying out loud'. You wouldn't use this in polite conversation or with superiors; it's for casual or heated moments with friends or family. The ったら form is similar but can also sound more childish or whiny. Both have the same meaning here, but ってば is a bit more assertive. The attachment is straightforward: just stick it onto the word you want to emphasize, like 田中ってば or もうってば. When using with verbs, you can attach to the te-form or past tense, like 言ってってば or 言ったら, to say 'like I said'. Avoid using it in writing or formal speech.