Debit order 5 days earlier than debicheck mandate

My debicheck mandate specifically states 20th of each month which is when i get paid. I understand most companies debit earlier in dec by sending an sms to advise, because i also get paid 5 days early i have had no issues over the years including clientelle legal. For the first time this yr, its the 15th Jan they have debited me and my last funds which i was meant to do groceries with this weekend for my family are gone. Clientelle legal has decided to help themselves before the agreed debit order date as per debicheck which is the 20th. I'm so angry and need answers on how we are going to survive till i get paid???