I have phoned inn several times a month for past 3+ years using my 12 year old phone number for many accounts some MC999 for other reasons without linking using the Contact Customer support with one time pass-code. Ebay has NEVER linked.
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I don't think it matters does it which number you call from, they may ask for the number attached to the account is all but you will have it to hand.
But i would withhold the number all the same
I have done the same thing, I have use my real phone number for total of about 10 calls over 2-3 years. They when ask if the phone number I am calling from is the same as my, I say "no".
I have even used Google voice to call ebay.
This is not a question, it is something the OP just wants to say to the world.