CUSTOMER DATA BASE AND SERVICE REMINDER DATE

I WORKING FOR SERVICE BASED BUSINESS . I WANT CUSTOMER DATA BASE MAINTAIN. SO I GIVE THE SEPARATE CUSTOMER ID NUMBER .ONCE ENTERED THE ID NUMBER DISPLAY FOR CUSTOMER FULL DATA ..THIS ONLY SEE FOR BUSINESS OWNER. THIS DATA IS NOT SHOW THE INVOICE .. THE CUSTOMER ID NUMBER IS SCANNING FOR BARCODE TYPE AND NUMERICAL NUMBER ANYTHING ONE SCAN FOR CUSTOMER DETAILS SHOW. THEN I WANT THE CUSTOMER SERVICE REMAINDER SETTING IS DATE BASED. NEST SERVICE AFTER 3 MONTHS . I WILL SET FOR TODAY THE SERVICE DATE . AUTOMATICALLY SEND THE REMINDER FOR AFTER THREE MONTHS THATS THE DATE DELIVERY TO SMS OR WHATSAPP THROUGH THE CUSTOMER .. THANK YOU