Hello penelope m and welcome to SayNoTo0870.com.
As sherbert says, some background information goes a long way.
Debenhams branches have sequential numbering for extensions. So if you find one, nearby numbers are also likely to go through to somewhere else in the store.
sherbert has given us a potentially large clue which is the fax number: 01865 255008
A search of the database for the company name
debenhams
returns many entries and within these I looked for 01865 numbers.
These is an unverified entry for the Oxford branch, 01865 25
50??:
- Electrical/Hardware=5036
- Fashion Accessories/Shoes=5053
- Menswear=5060
- Mac Cosmetics=5063
- Ladieswear=5072
- Cookware=5080
These are in the range of the fax number.
You could try one of these and ask to be put through (if the department you require isn't listed). If you can, I would appreciate if you can ascertain which department it is so it can be listed as such.
Alternatively, you could try a number at random. Remember you could be ringing a phone anywhere in the building including back room areas such as the staff room and the stock room. Sometimes you find that the main number for an office is the first in the range. I would guess that this number (the first in the sequence) is 01865 255000. As ever, you will have to try it and see.
Please do report back on what you find so I can list a suitable alternative(s).