Is this amount for an outstanding tab for a phone? If so, there is a system for it known as Tab Carryover as shown here:
https://www.koodomobile.com/en/help/carrying-your-tab-from-koodo-to-telus?srsltid=AfmBOop0XLPGwPufKL5jl3N92YWj63bqJZrPNyBYgUS32SuRu2TMreGS
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How to carry your Tab balance to TELUS
You can move your service to TELUS and carry over your Tab at any TELUS or Koodo store, authorized dealer, retailer, or over the phone with our sales and support teams. In some cases, a credit check may be required to activate your new TELUS service.
It’s not possible to carry over your Tab balance as part of an online order at this time.
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I assume then that this was not done? I’m not sure what needs to be done at this point since you’ve already switched over and this wasn’t done. If you like, I can flag a rep to confirm the best next step for you to get this correcte.d