Is it possible to retrieve old deleted txt msgs?

So my parents got mad at me cuz im kinda like talking to this guy who is like 21 and im only 16 & 3/4 and we're like rly into eachother, but they got mad cuz they think hes way too old for me and they told me i wasnt alowed to talk to him anymore and if i continued to theyd call the cops and crap, they claimed that they already knew about this guy and w.e even tho im pretty sure they didnt...but anyways, they said they were gunna retrieve all the old msgs that had been sent.....is this actually even possible if the msgs on the phone have all been deleted? Or are they just bluffing?....im with Bell Mobility if it matters at all.