Is civi automatically adding recurrence to contributions?
There was an issue that sounds very much like what you are describing (https://issues.civicrm.org/jira/browse/CRM-18277 that is marked as having been fixed as of 4.7.8), but I think you are saying that beyond the source of the first installment, there were actual recurring contribution records created and listed at the bottom of the contributions tab of a given contact that you then are not able to cancel? If that is the case, I would suggest opening a ticket on JIRA - I haven't seen any tickets in this regards.