They phone but end call straight away

Has anyone else had this scenario? So they call me to ask whether they could call me the next day, explaining it wasn’t a full assessment ‘just a sort of pre—assessment’ which I agreed to between 10.00 to 11.00. So I gathered all my notes and sat with my phone. Then flashed up their phone number but my phone didn’t ring(had volume turned up full). Tried to call them back but a messaged replied that they would try again. Today another call flashed up, no ringing despite me being with phone. Do you think this is a deliberate ploy of theirs to say they have tried to contact you but you don’t pick up the phone? Or am I just getting paranoid??? Many thanks!