Weak mobile phone signal

I was recently assigned to a new house just outside Hamilton city, probably less than 10 minutes drive going towards Morrinsville and Cambridge.  Our role is to support youth with intellectual disabilities, 24/7.  There are times when I'm assigned to do a sleepover.  And when I'm inside the house there's no signal from my mobile phone.  I have to go outside to get a clear signal from my service provider.  I don't mind if it's during the day but at night it's such a great hassle to get up and go out, and it's practically freezing this time of the year.  And it's not even winter yet!