Go to econet, get an affidavit form. Get a copy of your ID, you Sim Certificate with your pin and puk number and proof of residence.
Fill out as per their instructions and you are done
see below direct from ewz.
"Kindly visit an Econet to change ownership of the line with your ID (original and photocopy), SIM card certificate and proof of residence.
You will be asked to complete an affidavit form, stating the reasons behind the change of line details request. After this has been signed by the Commisioner of Oaths, it is submitted together with the documents listed above. Afterwhich the details of your line may be changed. Thanks Buddie!"