If it’s only a bigger or smaller package within the same service, it will not affect the data file, however to be safe always keep a backup or you have individual backup plan already activate on the account.

Further, if it’s a change of services like web hosting to email hosting or other way, all the old data will be deleted as essentially these will be new services altogether.

Therefore we strongly recommend to get the backup yourself or have a paid auto backup service activated on your account.