Ibm websphere MQ; rollback/un commit not happening

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C#3.5

API

using IBM.WMQ;

MQQueue queue;
MQMessage mq_msg;
MQGetMessageOptions gmoptions;
MQQueueManager oMQQMGR;

mq_msg = new MQMessage();
queue.Get(mq_msg, gmoptions);
string message_text = mq_msg.ReadString(mq_msg.DataLength);

oMQQMGR.Commit();

Once read, is there any option to RollBack/Un Commit ?

What I have tried:

I am not performing the commit as the Biz logic fails, why the item is not coming back to queue? Once read, is there any option to RollBack/Un Commit. Options are given for rollback and Non commit, but not really happening.

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