Pretty hard to tell anything from that photo but the paired leaves and their shape might indicate a clematis. If so, not gonna do well in that pot for long.

gardengal48 - do you think it could be Thunbergia alata?

I guess it's possible, floral :-) Sure hard to see clearly. The apparent serrations may be a little indicative of that vine but the leaf shape doesn't look quite right. And to be honest, I've never seen one that was so devoid of foliage so maybe the overall poor condition of the vine is altering my judgement.

And I wouldn't exactly consider Thunbergia alata's flowers as "big" :-) Did they say what color the flowers might be? That could help.