Spire 158% increase

We are renovating a home in south st Louis . No one is living there but we keep the heat very low so pipes don’t freeze. Last month Spire bill was $39.73. This month $108.90. Wtf? I’m calling in Monday about this winter usage charge and how my natural gas charge went from $3.28 to $38.12!! Can anyone enlighten me??? We lived in the city for over 20 years and never experienced this.