The call ended abruptly.
( ( The call ) ( ( ended abruptly ) . ) )
(ROOT (S (NP (DT The) (NN call)) (VP (VBD ended) (ADVP (RB abruptly))) (. .)))
The caller was unaware that the call would cut off. 
( ( The caller ) ( ( ( was unaware ) ( that ( ( the call ) ( would ( cut off ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN caller)) (VP (VBD was) (ADJP (JJ unaware)) (SBAR (IN that) (S (NP (DT the) (NN call)) (VP (MD would) (VP (VB cut) (PRT (RP off))))))) (. .)))