So, he apparently tried calling, but the person on the other end turned out to be a problem.
Literal
So, call-[try-てみた] [seems-らしい] [but-んだけど], that call-destination [gen-の] partner [topic-ってのが] problem [copula-だった] [emph-のよ].
で at the start is a continuer/discourse marker 'so / and then,' stripped down from それで. ~てみた is 'tried X-ing.' ~らしいんだけど is the hearsay + explanatory + contrastive stack — 'I hear that X, but...'. 電話先 'call-destination' is a compound noun for 'the place/person you're calling.' ってのが is the casual contraction of というのが, marking a new topic / the thing that turns out to be significant. ~のよ is the feminine explanatory emphatic ending.