Must be difficult for you !! My experience as compared to yours: I have yet to deal with such a customer Alhamdulillah.
-If they call at odd hours, I politely tell them the local time and the timings suitable for me to talk to them and never had a problem thereafter.
-I let them know I would start working their order when I get the payment and will complete by 3 or 4 or 5 weeks (depending on my prior commitments,etc) and usually keep them updated with pictures after the dyeing/kaam/embroidery is done and keep telling the approximate time when the order will be completed so there is no haunting from them with numerous emails/texts.
-this might sound strange but I hardly have people haggling or asking to bring prices down or confronting by telling that they saw a particular thing for 500rs which I am selling for 1500rs Alhamdulillah..not even for bridals ! So I think this solely depends on having justified and legit profit margins since in this era of internet,etc, most of the people are well aware of what a particular thing costs and know we,vendors need to keep a commission/profit margins for all the running as well so they hardly negotiate unless they feel the need to do it.
-about bad reviews/remarks, I have seen them them only when vendors make a blunder with the order and hide away the response can be exaggerated at times but then,no one complains pointlessly. They only get on to public bashing when we ignore their PMs,emails or FB msgs, no ?
-about the payment,not good for business but I am not particular about getting the payment before I start with the work with my regular/old customers. My aim is to complete it in time for the event and except for once or twice, NO one ran away with the money so far Alhamdulillah X infinity. But that’s me !! For all vendors,if you tell the customers in the beginning upfront and clearly that you wont change the order once finalise and wont start working on it unless you get full/half of the payment (whatever your policy is)and make it clear that the time you committed to complete the order will start AFTER the money is sent, that should make you justified if you refuse to go ahead with the order if the policies specified are not followed.
SO, I think all the mishaps and hiccups in the ordering process can be sorted by proper approach.