It continues. Canceling your airtime contract does not settle a phone financed over 24 months.
German providers usually split a subsidised handset into a separate purchase contract with its own instalments. It appears on your invoice as its own line, often labeled Ratenzahlung or Gerätefinanzierung.
People discover this months later, from another continent.
Find the instalment line on your invoice.
Contact the provider about settling the remaining balance in one payment before you leave.
It continues. Canceling your airtime contract does not settle a phone financed over 24 months.