This should be approved based system as to prevent false user onboarding. Need to get some identification document or introduce Caller verification.
This is normal registration and we can use referal link from Service provider to ease the linking process between service provider and Consumer.
Create a link between Consumer and Service Provider. 1 SP can deliver to multiple Con.1 Con can buy from multiple SP.
SP user will get option to delivery linked cons only. They will be sorted in based on their address within the system and displayed to SP. SP will select the user and verify the quantity of product and hit delivered.
By end of each month, user will get bill and payment option, incase user wants to pay cash, user can choose to select cash option and confirm. This will update SP.