It depends on your contract with Odido. If you are free to switch (usually after one or two years), then go to KPN “overstappen”: https://www.kpn.com/mobiel-abonnement/overstappen.htm

Best @JulietHolland 

With a prepaid connection with Odido, you can easily switch to a KPN subscription.
You simply take your own 06 number with you by requesting number portability when ordering your KPN mobile subscription.

Go through this link: Mobiel abonnement (sim-only) bestellen
to the page where you can request a SIM-only (mobile subscription) from KPN.

First select YES for KPN Combivoordeel (Step 1), because you already purchase internet and television from KPN.
In Step 2, choose whether you want unlimited calling or a calling bundle of 200 minutes.
In Step 3, choose the amount of data credit
In Step 4, choose the term of your contract (month, 1 year or 2 years)
In Step 5, choose which SIM card you wish to receive, depending on the smartphone you currently have.

Choose continue, then fill in your personal details and request number portability.

In most cases, number portability from prepaid to a subscription is arranged within 3 to 5 working days.
KPN ensures that you receive their SIM card on time, before your 06 number is transferred to KPN.

Is everything clear to you now?
If not, feel free to ask.