Handed over because of oneplan

I was handed over because of one plan. My son got hospitalized last year April, bill was not settled to the fullest. I received calls from the hospital so I went back to liaise with the medical insurance in regards to the amount that was not paid. They said the amount was settled and they sent me a statement showing they paid, when I told them there's an amount that is not paid and can they please follow up from the hospital, well they didnt, maybe i was not an important client. Unfortunately I lost my job and had to cancel my cover last year November, mind you this matter of owing the hospital is not settled. Now the hospital has handed me over for non payments. I tried getting in touch with the medical several times for assistance but no luck. I tried again today since this happened while I was covered, the person I talked to on whatsapp was not friendly at all, not helpful at all. I asked him/her for them to call me. Instead the answer was I should tell the hospital to phone them. What kind of service is that? But if I told that person I wanted a cover she/he would have called me instantly. How am I suppose to pay the hospital as I'm not working? One plan knew there is an amount that was not paid, why didn't they communicate with me? What am I to do now coz your "friendly staff" ain't helping