Give the user time she/he asked for. After that, do not wait for user to call you. Send her a polite reminder WhatsApp or text message giving little more information on why s/he should patronize you. If the customer still does not respond, give a call during the suitable hours of the day (say 8am to 8pm).

Remember, users check out more than one business before they decide whom to patronize. She may not patronize you this time, but building a good relationship is always a good idea. After 3 to 5 calls and messages, if user is not responding, leave her a polite message, thank her for showing interest and tell her she can contact you if she needs similar service in the future.