A cron is sending thousands of emails

Hello, since a while, and it was really hard long and painful to understand, my emails were not coming anymore. In fact, my account was blocked because of thousands mails sent.

Not I found why :

I receive this at least every minute :

Cron <asterisk@voip> [ -x /var/lib/asterisk/bin/schedtc.php ] && /var/lib/asterisk/bin/schedtc.php

InvalidArgumentException: Unknown or bad timezone (default) in file /var/www/html/admin/libraries/Composer/vendor/nesbot/carbon/src/Carbon/Carbon.php on line 252
Stack trace:
 1. InvalidArgumentException->() /var/www/html/admin/libraries/Composer/vendor/nesbot/carbon/src/Carbon/Carbon.php:252
 2. Carbon\Carbon->safeCreateDateTimeZone() /var/www/html/admin/libraries/Composer/vendor/nesbot/carbon/src/Carbon/Carbon.php:291
 3. Carbon\Carbon->__construct() /var/www/html/admin/libraries/Composer/vendor/nesbot/carbon/src/Carbon/Carbon.php:336
 4. Carbon\Carbon->now() /var/www/html/admin/modules/calendar/Calendar.class.php:63
 5. FreePBX\modules\Calendar->setTimezone() /var/www/html/admin/modules/timeconditions/bin/schedtc.php:65

All my modules and system are up-to-date.

It's kind of urgent to at least tell me how to REMOVE mail sending for this. My providers wants to ban me.