We keep paying in advance BUT policy stay in arrea

My mother have her policy with AVBOB for several years now. We sometimes pay for 3 - 4 months ahead. Now suddenly I received an sms saying policy will lapse as it is in arrears.<br> <br> How is this possible as I did pay in Dec 2015 for 4 months and again in April 2015 for 3 months. This is now becoming a great concern as it seems we don't pay. I remember my late dad also paid his policy every month on 25th. The December he passed we were informed that his policy is in arrears. Howe does this happen ???<br> <br> I need a statement for my mothers policy from the day it started ASAP...