# How to retain customers when transitioning from a GSM Gateway to IP Telephony

If you have a GSM gateway, we suggest that you temporarily set up incoming call forwarding to a new number to make the transition to IP telephony easier.

**How it will look like for the client:**

1. After switching to IP telephony, we update the information on all resources and send out a mailing list to customers with a message about the new number.
2. Customers who call the old number out of habit will be automatically redirected to the new one (this is done imperceptibly for the customer).
3. Outgoing calls to the customer will be made from the new number.

This will allow your customers to gradually get used to the new company number, while maintaining continuous communication during the transition period.

{% hint style="warning" %}
**The disadvantage** is that you will have to pay for each incoming call with call forwarding as an outgoing call according to your tariff plan.
{% endhint %}

Call forwarding terms and conditions from providers (click on the link in the name of provider to read more information):

1. **Call forwarding cost**
   1. [Київстар](https://kyivstar.ua/business/mobile/services/distance-call-forwarding) - free of charge
   2. [Lifecell](https://www.lifecell.ua/uk/poslugi/katalog/upravlinnia-dzvinkamy/) - 0.21 UAH / call
   3. [Vodafone](https://www.vodafone.ua/services/pereadresaciya) - free of charge
   4. [Укртелеком ](https://b2b.ukrtelecom.ua/news/ostavatsya-na-svyazi-72) - free of charge
   5. [Vega](https://vega.ua/for_office/call_forward) - free of charge
2. **Cost of incoming calls -** as the cost of outgoing calls according to your tariff plan
3. **Setting up the service** 
   * Activate: \*\*21\*phone number#
   * Deactivate: #21#


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