UNFAIR OBF REJECTION & POOR SERVICE

I upgraded my cellphone contract on the 2 December 2019 only to fiupgradednd out the phone was faulty,(overheating and had no signal) so i took it back to the store within the seven day (08/01/ 2021 ) period for it to be exchanged on the OBF options but to my suprise it was rejected for OBF but upon collection when i went to collect it on the 29 it was still over heating so it's only the signal problem that was fixed but the phone was still overheating so i re-booked the phone for the issue to be rectified but when doing a follow up i was told that it was sent to the external repair center for it to be fixed so my query is what should i be given a repaired phone which i bought back within the seven day period? If my OBF was rejected on fair and valid reason why was it repaired n i am not given a new phone....NB today it's the 21/01/2021 i still don't have a phone....