Which delivery service to choose for an online store?

Question

API

Good afternoon!
There are 3 questions:
1. Which one to choose?
2. And how is the cost calculated on the site?
3. Is there any service that combines several courier services APIs into 1 at once (so that each service does not write its own script)?
We have:
Several warehouses in different regions of the Russian Federation The
average weight of a parcel is 5 kg
We want:
Delivery to all cities of Russia
Cash on delivery (convenient for 98% of buyers)
Delivery time - no more than a week.
Developed API for integration with the online store
Manager with broad powers The
same cost of delivery throughout Russia (For example, 250 rubles)
We have money from customers in a couple of days.
Undelivered parcels are returned after a week. For free. Specifies the reason for the return.
Found www.sheepla.ru who ever worked with her? What can you say about her?

Answer 1

Well, you have requirements =) Try SDEK (not a bad API), DPD is not sure about the deep API, but there is a cost calculation! Also, as an option, you can use SPSR, there is also a 100% cost calculation.

Answer 2

I recommend:
TopDelivery is a more private solution. There is an API.
Delivia is a solution that integrates several delivery services through one IT system. Now we are moving to Delivey, so far everything is fine.