Thats beyond what Ive seen before this. Im so sorry it happens to you. Seems you have bought it from Printemps? Since Chanel boutique & the departmental store (example: printemps & layafayette) has a different store policy, probably its best to go back go printemps.
Chanel boutique only allows exchanges & store credit within a timeframe, where as departmental store usually accept return. Check your receipt on this. However, since you bought from the departmental store&still within the return/exchange period, probably the chanel boutiques would ask you to reach Printemps to sort this out first. If theres any way for you to visit the store, thats would be the most ideal. Face to face communication is more effective for this kind of cases.
Keep following up with the person via email. And try to get hold of Chanel Printemps. Departmental store chanel based my experience is hard to be contacted since you go through the departmental main line, then only they shift the call to chanel store, so you have to be persevere.
I would advice you to try get hold of them within the exchange/return timeframe, since the bag seems to have problem structurally. Be ready to have your story of how/what/when you notice it happened, since its such a rare case this happen unless the bag has been crushed over use. Probably thats why the boutiques you approached was shocked since they never seen the bag like that from a short time use. Other than the store you bought it from will not do exchange/store credit on bags with defect.
After the exchange/return time frame, Chanel could only honor you the repair service, which they might/might not be able to do, depending on Paris assesment. If they do it will take a very long time, since its a structural problem. You can send chanel bags for repair via any store/Boutiques since all bags will go to Paris for further assessment for serious cases like this. Some members here were given store credit on bags that had not been able to restored after the bag been sent to Paris for assessment. However the bag was purchased & sent for service at the same boutiques store, so probably its easier for them to be given store credit.
Persevere & I really hope you will be able to sort this out soon. All the best..