I have been screwed over by RE many times. My advice, do EVERYTHING via email and not through phone calls and also keep any and all pieces of paper the RE sends/gives you, no matter how unimportant it might seem at the time. This way, if things go bad in the future, you have written, dated proof that you have communicated the problem and asked for it to be fixed and it was the RE who failed to follow it up. Phone calls are not documented and there is no way to prove you have (calmly and politely) tried to contact the agent). Trust me, it might sound a bit extreme or silly, but come end of lease you might be thankful you have all this paperwork and proof.
Im glad you are getting your hot water sorted tomorrow