In spite of the heavy rain,we went to school on time
=>Although........ it rained heavily, we went to school on time..................................................
he didn't have any money, but he bought an expensive mobile phone
=>Although.............he didn't have any money, he bought an expensive mobile phone...........................................................................
They had to pay a large bill because they didn't use electricity economically
=>They didn't use electricity economically,................... use electricity economically, so they had to pay a large bill...................................

1Although it was raining heavily, we went to school on time.
2Although he didn't have any money, he bought an expensive mobile phone.
3They didn't use electricity economically, so they had to pay a large bill.