@milimi,
The previous posters have, I suggest, missed the point. There is an older meaning of 'dub', predating modern sound recording. The sentence is clearly using the word in that older sense:
Give an name or nickname to (someone or something)
"the media dubbed anorexia “the slimming disease.”
synonyms: nickname, call, name, label, christen, term, tag, entitle, style
The talks are being dubbed (called, termed, described as) "last chance" talks.